Make MPEG2fixup::ProcessVideo return int

I'm not 100% sure what the original author was trying to do here, but this
code is broken.  Returning 0, 1, -1 for a bool makes no sense, and comparing
bool < 0 makes even less sense.  Rather than trying to unravel what he was
trying to do, let's make this a simple int return so the return codes should
have some effect.

Fixes #9549
(cherry picked from commit 0234965)

mythtv/programs/mythtranscode/mpeg2fix.cpp

@@ -836,7 +836,7 @@ void MPEG2fixup::AddSequence(MPEG2frame *frame1, MPEG2frame *frame2)
     }
 }
 
-bool MPEG2fixup::ProcessVideo(MPEG2frame *vf, mpeg2dec_t *dec)
+int MPEG2fixup::ProcessVideo(MPEG2frame *vf, mpeg2dec_t *dec)
 {
     int state = -1;
     int last_pos = 0;

mythtv/programs/mythtranscode/mpeg2fix.h

@@ -172,7 +172,7 @@ class MPEG2fixup
     int AddFrame(MPEG2frame *f);
     int InitAV(const char *inputfile, const char *type, int64_t offset);
     void ScanAudio();
-    bool ProcessVideo(MPEG2frame *vf, mpeg2dec_t *dec);
+    int ProcessVideo(MPEG2frame *vf, mpeg2dec_t *dec);
     void WriteFrame(const char *filename, MPEG2frame *f);
     void WriteFrame(const char *filename, AVPacket *pkt);
     void WriteYUV(const char *filename, const mpeg2_info_t *info);