nir: fix missing nir_lower_pntc_ytransform.c in the makefile

Fixes: 33fd9e5d "nir: account for point-coord origin when lowering it"
Signed-off-by: Danylo Piliaiev <dpiliaiev@igalia.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Part-of: <!8308>