i965: make sure check_and_emit_atom gets inlined

i965: make sure check_and_emit_atom gets inlined

Improves performance of 3DMark "Ice Storm Unlimited" benchmark
by 1-2% on Apollolake (on Android-IA using clang 3.8.256229).

Change is based on the performance profiling work and results
by Aravindan Muthukumar and Yogesh Marathe.

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Signed-off-by: Aravindan Muthukumar <aravindan.muthukumar@intel.com>
Signed-off-by: Yogesh Marathe <yogesh.marathe@intel.com>
Reviewed-by: Scott D Phillips <scott.d.phillips@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>