Merge pull request #3242 from phire/less-warnings

XFMem: Don't warn on writes of zero to unknown registers.

Source/Core/VideoCommon/XFStructs.cpp

@@ -184,6 +184,7 @@ static void XFRegWritten(int transferSize, u32 baseAddress, DataReader src)
 		case 0x1017:
 
 		default:
+			if (newValue != 0) // Ignore writes of zero.
 				WARN_LOG(VIDEO, "Unknown XF Reg: %x=%x", address, newValue);
 			break;
 		}