r300g/compiler: Prevent regalloc from swizzling texture operands v2

https://bugs.freedesktop.org/show_bug.cgi?id=63520

NOTE: This is a candidate for the stable branches.

Reviewed-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 24fa43675f32bc81c7252f3ddce4c80ed8c7737d)
nvc0: allow frame dropping in h264

The only reason the checks existed were paranoia, when I first
wrote the code I wasn't sure it was correct. Now that I am,
the asserts triggered when XBMC was dropping frames, so remove it.

NOTE: This is a candidate for the 9.1 branch.
(cherry picked from commit bf95ca7de0c02a00a75d1d5e2693a33b68ff784d)