ttn: unconditionally call nir_shader_gather_info
Mesa st always calls this and thus some drivers expect to have the info. This fixes assertions in NineTests on iris (tested with BDW GT2).
Closes: #6946
See !17851 (closed) for previous fix attempt (there the nir_shader_gather_info was called instead in iris_finalize_nir) and where @llandwerlin made the argument this should be fixed in ttn instead.
CC @speles Can you check that this also fixes all the issues with your HW?