Sas: Correct calculation of VAG end.

Not sure why everything is negative one indexed, but this has to be right.
Otherwise, we end up decoding 16 bytes outside of the size of the buffer.

This may reduce slight garbage noise after sound effects.

Core/HW/SasAudio.cpp

@@ -106,7 +106,7 @@ void VagDecoder::DecodeBlock(u8 *&read_pointer) {
 	s_2 = s2;
 	curSample = 0;
 	curBlock_++;
-	if (curBlock_ == numBlocks_) {
+	if (curBlock_ == numBlocks_ - 1) {
 		end_ = true;
 	}