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>
(cherry picked from commit 30ead72e80e5b7ba5c5dfc46261b4d249f4fa382)

.pick_status.json

@@ -874,7 +874,7 @@
         "description": "nir: Allow nir_texop_tg4 in implicit derivative",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "48158636bf1b0e62ebab4835e1f474866a34c6fe",
         "notes": null

src/compiler/nir/nir.c

@@ -3133,6 +3133,8 @@ 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;
    }