SPU: Fix DC filter types and clamping

Fix wrong type being used for dc filter state.

The filter seems to introduce some small amount of gain, so we need to
clamp it.

pcsx2/SPU2/Mixer.cpp

@@ -691,8 +691,8 @@ __forceinline
 	// Edit: I'm sorry Jake, but I know of no good audio system that arbitrary distorts and clips
 	// output by design.
 	// Good thing though that this code gets the volume exactly right, as per tests :)
-	Out = clamp_mix(Out);
 	Out = DCFilter(Out);
+	Out = clamp_mix(Out);
 	SndBuffer::Write(StereoOut16(Out));
 
 	// Update AutoDMA output positioning

pcsx2/SPU2/defs.h

@@ -514,7 +514,7 @@ extern u16 InputPos;
 // SPU Mixing Cycles ("Ticks mixed" counter)
 extern u32 Cycles;
 // DC Filter state
-extern StereoOut16 DCFilterIn, DCFilterOut;
+extern StereoOut32 DCFilterIn, DCFilterOut;
 
 extern s16 spu2regs[0x010000 / sizeof(s16)];
 extern s16 _spu2mem[0x200000 / sizeof(s16)];

pcsx2/SPU2/spu2sys.cpp

@@ -37,7 +37,7 @@ V_CoreDebug DebugCores[2];
 V_Core Cores[2];
 V_SPDIF Spdif;
 
-StereoOut16 DCFilterIn, DCFilterOut;
+StereoOut32 DCFilterIn, DCFilterOut;
 u16 OutPos;
 u16 InputPos;
 u32 Cycles;