intel/compiler: Silence unused parameter warning in brw_interpolation_map.c

intel/compiler: Silence unused parameter warning in brw_interpolation_map.c

The parameter is never used, and it's not part of a common interface
idiom.  Remove it.

src/intel/compiler/brw_interpolation_map.c: In function ‘brw_setup_vue_interpolation’:
src/intel/compiler/brw_interpolation_map.c:62:59: warning: unused parameter ‘devinfo’ [-Wunused-parameter]
                             const struct gen_device_info *devinfo)
                                                           ^~~~~~~

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>