brw: fix type conversion in tex operation params

Fix a bunch of tests in dEQP-VK.glsl.texture_gather.* on Xe2+

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: bddfbe7fb1 ("brw/blorp: lower MCS fetching in NIR")
Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37532>

src/intel/compiler/brw_from_nir.cpp

@@ -7373,13 +7373,9 @@ brw_from_nir_emit_texture(nir_to_brw_state &ntb,
          src_type = BRW_TYPE_D;
          break;
 
-      case nir_tex_src_backend1:
-      case nir_tex_src_backend2:
-         src_type = BRW_TYPE_UD;
-         break;
-
       default:
          src_type = default_src_type;
+         break;
       }
 
       switch (instr->src[i].src_type) {