i965: Don't flag BRW_NEW_SURFACES unless some push constants are dirty.

i965: Don't flag BRW_NEW_SURFACES unless some push constants are dirty.

Due to a gaffe on my part, we were re-emitting all binding table entries
on every single draw call.  The push_constant_packets atom listens to
BRW_NEW_DRAW_CALL, but skips emitting 3DSTATE_CONSTANT_XS for each stage
unless stage_state->push_constants_dirty is true.  However, it flagged
BRW_NEW_SURFACES unconditionally at the end, by mistake.

Instead, it should only flag it if we actually emit 3DSTATE_CONSTANT_XS
for a stage.  We can move it a few lines up, inside the loop - the early
continues will skip over it if push constants aren't dirty for a stage.

With INTEL_NO_HW=1 set, improves performance of GFXBench5 gl_driver_2
on Apollolake at 1280x720 by 1.01122% +/- 0.470723% (n=35).

Reviewed-by: Rafael Antognolli <rafael.antognolli@intel.com>