freedreno/ir3: fix fixing-up register footprint

freedreno/ir3: fix fixing-up register footprint

It isn't just vertex shaders that need to fixup reg footprint for inputs
populated before shader starts.

This problem showed up with compute shaders.  If you have (for example)
a localregid sysval, but only the .x component is used, the hw still
writes the .yz components, which could overflow into other threads
causing corruption.  Showed up in cl cts 'basic/test_basic intmath_int'.
But in theory the same problem could crop up elsewhere.

Signed-off-by: Rob Clark <robdclark@gmail.com>