intel,nir: Lower TXD with min_lod when the sampler index is not < 16

intel,nir: Lower TXD with min_lod when the sampler index is not < 16

When we have a larger sampler index, we get into the "high sampler"
scenario and 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.

Fixes: cb98e0755f8d "intel/fs: Support min_lod parameters on texture..."
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>