i965: Rename brw_wm_sampler_state.c to brw_sampler_state.c.

i965: Rename brw_wm_sampler_state.c to brw_sampler_state.c.

When the driver was originally written, it only supported texturing in
the pixel shader backend; vertex and geometry shader texturing came much
later.  Originally, the pixel shader was referred to as "WM" (the
Windowizer/Masker unit).  So, this code happened to only be relevant for
the WM stage, at the time.

However, sampler state really applies to all stages, so putting "wm" in
the filename doesn't make sense.  I dropped it in gen7_sampler_state.c;
at this point the asymmetry just trips people up.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>