i965/fs: Allow SIMD16 on pre-SNB when try_replace_with_sel is successful

i965/fs: Allow SIMD16 on pre-SNB when try_replace_with_sel is successful

If try_replace_with_sel is able to replace the flow control with a SEL
instruction, then there is no flow control... failing SIMD16 because
of nonexistent flow control is wrong.

No piglit regressions on any i965 platform in Jenkins.

total instructions in shared programs: 4382707 -> 4382707 (0.00%)
instructions in affected programs:     0 -> 0
helped:                                0
HURT:                                  0
GAINED:                                2089
LOST:                                  0

No other platforms affected in shader-db.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>