On Gen7, we have to split shuffles into two MOVs for 64-bit types so we
can't handle source modifiers. On Gen12.5, we have to use integer types
all the time so we can't use them there either. Fixing that will be a
different commit but it interacts with this one.
Fixes: 90c9f29518 "i965/fs: Add support for nir_intrinsic_shuffle"
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9068>