intel/fs: Delete a TODO about using brw_F32TO16.

We can just use the new builder helpers to get the optimization
advantages of a MOV on Gfx8+ while also getting the necessary F32TO16
on Gfx7.x and yet not worry too hard about it.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21783>

src/intel/compiler/brw_fs_nir.cpp

@@ -1070,17 +1070,8 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr,
       if (BRW_RND_MODE_UNSPECIFIED != rnd)
          bld.emit(SHADER_OPCODE_RND_MODE, bld.null_reg_ud(), brw_imm_d(rnd));
 
-      /* In theory, it would be better to use BRW_OPCODE_F32TO16. Depending
-       * on the HW gen, it is a special hw opcode or just a MOV, and
-       * brw_F32TO16 (at brw_eu_emit) would do the work to chose.
-       *
-       * But if we want to use that opcode, we need to provide support on
-       * different optimizations and lowerings. As right now HF support is
-       * only for gfx8+, it will be better to use directly the MOV, and use
-       * BRW_OPCODE_F32TO16 when/if we work for HF support on gfx7.
-       */
       assert(type_sz(op[0].type) < 8); /* brw_nir_lower_conversions */
-      inst = bld.MOV(result, op[0]);
+      inst = bld.F32TO16(result, op[0]);
       break;
    }