Use faster CheckGatherPipe from JIT.

We don't need to profile explicit calls to CheckGatherPipe: we aleady know
where they are. Skip profiling, and explciitly insert an exception check.

While I'm here, get rid of unused code in JitIL.

Source/Core/Core/PowerPC/Jit64IL/JitIL.cpp

@@ -361,11 +361,6 @@ static void ImHere()
 
 void JitIL::Cleanup()
 {
-	if (jo.optimizeGatherPipe && js.fifoBytesThisBlock > 0)
-	{
-		ABI_CallFunction((void *)&GPFifo::CheckGatherPipe);
-	}
-
 	// SPEED HACK: MMCR0/MMCR1 should be checked at run-time, not at compile time.
 	if (MMCR0.Hex || MMCR1.Hex)
 		ABI_CallFunctionCCC((void *)&PowerPC::UpdatePerformanceMonitor, js.downcountAmount, jit->js.numLoadStoreInst, jit->js.numFloatingPointInst);