nir: Allow nir_texop_tg4 in implicit derivative

This allow us to invoke the quad helper.

v2: (Georg)
- Add check for is_gather_implicit_lod

Fixes: 48158636bf ("nir: add is_gather_implicit_lod")
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27447>

src/compiler/nir/nir.c

@@ -3145,6 +3145,8 @@ nir_tex_instr_has_implicit_derivative(const nir_tex_instr *instr)
    case nir_texop_txb:
    case nir_texop_lod:
       return true;
+   case nir_texop_tg4:
+      return instr->is_gather_implicit_lod;
    default:
       return false;
    }