nir/lower_shader_calls: remove CF before nir_opt_if

Otherwise, opt_if_simplification() can attempt to insert an inot after a
jump.

Fixes RADV compilation of a Cyberpunk 2077 pipeline with
PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: mesa-stable
Part-of: <mesa/mesa!27193>