LoongArch: KVM: Fix unknown register name 'v0' in asm

According to KVM documention for LoongArch, 'v0' should be 'a0'.
And 'a0' has been there upstream.

Fix follow compile errors with clang-19:

In file included from ./include/uapi/linux/kvm_para.h:41:
./arch/loongarch/include/asm/kvm_para.h:44:24: error: unknown register name 'v0' in asm
   44 |         register long ret asm("v0");
      |                               ^
./arch/loongarch/include/asm/kvm_para.h:59:24: error: unknown register name 'v0' in asm
   59 |         register long ret asm("v0");
      |                               ^
./arch/loongarch/include/asm/kvm_para.h:76:24: error: unknown register name 'v0' in asm
   76 |         register long ret asm("v0");
      |                               ^
./arch/loongarch/include/asm/kvm_para.h:94:24: error: unknown register name 'v0' in asm
   94 |         register long ret asm("v0");
      |                               ^
./arch/loongarch/include/asm/kvm_para.h:114:24: error: unknown register name 'v0' in asm
  114 |         register long ret asm("v0");
      |                               ^
./arch/loongarch/include/asm/kvm_para.h:135:24: error: unknown register name 'v0' in asm
  135 |         register long ret asm("v0");
      |                               ^
6 errors generated.

Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e33bda7ee50c3c20d80f5ca6dc5ca2cd37863518
Signed-off-by: Mingcong Bai <[email protected]>
Signed-off-by: WangYuli <[email protected]>

arch/loongarch/include/asm/kvm_para.h

@@ -41,7 +41,7 @@ struct kvm_steal_time {
  */
 static __always_inline long kvm_hypercall(u64 fid)
 {
-	register long ret asm("v0");
+	register long ret asm("a0");
 	register unsigned long fun asm("a0") = fid;
 
 	__asm__ __volatile__(
@@ -56,7 +56,7 @@ static __always_inline long kvm_hypercall(u64 fid)
 
 static __always_inline long kvm_hypercall1(u64 fid, unsigned long arg0)
 {
-	register long ret asm("v0");
+	register long ret asm("a0");
 	register unsigned long fun asm("a0") = fid;
 	register unsigned long a1  asm("a1") = arg0;
 
@@ -73,7 +73,7 @@ static __always_inline long kvm_hypercall1(u64 fid, unsigned long arg0)
 static __always_inline long kvm_hypercall2(u64 fid,
 		unsigned long arg0, unsigned long arg1)
 {
-	register long ret asm("v0");
+	register long ret asm("a0");
 	register unsigned long fun asm("a0") = fid;
 	register unsigned long a1  asm("a1") = arg0;
 	register unsigned long a2  asm("a2") = arg1;
@@ -91,7 +91,7 @@ static __always_inline long kvm_hypercall2(u64 fid,
 static __always_inline long kvm_hypercall3(u64 fid,
 	unsigned long arg0, unsigned long arg1, unsigned long arg2)
 {
-	register long ret asm("v0");
+	register long ret asm("a0");
 	register unsigned long fun asm("a0") = fid;
 	register unsigned long a1  asm("a1") = arg0;
 	register unsigned long a2  asm("a2") = arg1;
@@ -111,7 +111,7 @@ static __always_inline long kvm_hypercall4(u64 fid,
 		unsigned long arg0, unsigned long arg1, unsigned long arg2,
 		unsigned long arg3)
 {
-	register long ret asm("v0");
+	register long ret asm("a0");
 	register unsigned long fun asm("a0") = fid;
 	register unsigned long a1  asm("a1") = arg0;
 	register unsigned long a2  asm("a2") = arg1;
@@ -132,7 +132,7 @@ static __always_inline long kvm_hypercall5(u64 fid,
 		unsigned long arg0, unsigned long arg1, unsigned long arg2,
 		unsigned long arg3, unsigned long arg4)
 {
-	register long ret asm("v0");
+	register long ret asm("a0");
 	register unsigned long fun asm("a0") = fid;
 	register unsigned long a1  asm("a1") = arg0;
 	register unsigned long a2  asm("a2") = arg1;