intel,nir: Lower TXD with a bindless sampler

intel,nir: Lower TXD with a bindless sampler

When we have a bindless sampler, we need an instruction header.  Even in
SIMD8, this pushes the instruction over the sampler message size maximum
of 11 registers.  Instead, we have to lower TXD to TXL.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>