[mythtv] MythMusic fails to compile on x86_64

[Kyle Schlansker]

Naturally it is some sort of assembly problem.  When mmx is enabled,
the compile fails on mythmusic/goom/filters.c and when mmx is disabled
it fails on mythmusic/goom/zoom_fitler_xmmx.c.

I've tried changing all the references to eax to rax as well as other
register changes, but I don't know the major changes needed for x86_64
assembly stuff.

Any suggestions?

-- Kyle S.