i965/fs: Fix test for smearing enabled on an instruction.

i965/fs: Fix test for smearing enabled on an instruction.

We were expanding the live range too far, breaking register_coalesce_2()
and compute_to_mrf() on 16-wide shaders.  Turning it back on improves
GLB2.7 performance by 0.239355% +/- 0.0850649% (n=398). shader-db stats
are:

total instructions in shared programs: 1627211 -> 1609262 (-1.10%)
instructions in affected programs:     450351 -> 432402 (-3.99%)

While 33 new 16-wide shaders are gained, 70 are lost.  Despite that,
tropics (the app that lost the most 16-wide) shows a .41% +/- .16%
(n=7/8, first-run outlier removed) performance improvement on my HSW.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>