drm/arise: donot assigning value of variable of type to itself

Fix follow compile errors with clang-19:

drivers/gpu/drm/arise/linux/os_interface.c:1995:10: error: explicitly assigning value of variable of type 'unsigned long' to itself [-Werror,-Wself-assign]
 1995 |     base = base;
      |     ~~~~ ^ ~~~~
drivers/gpu/drm/arise/linux/os_interface.c:1996:10: error: explicitly assigning value of variable of type 'unsigned long' to itself [-Werror,-Wself-assign]
 1996 |     size = size;
      |     ~~~~ ^ ~~~~
2 errors generated.

Signed-off-by: WangYuli <[email protected]>

drivers/gpu/drm/arise/linux/os_interface.c

@@ -1992,8 +1992,6 @@ int gf_mtrr_del(int reg, unsigned long base, unsigned long size)
     err =  mtrr_del(reg, base, size);
 #else
     /* avoid build warning */
-    base = base;
-    size = size;
     arch_phys_wc_del(reg);
     err = 0;
 #endif