ttn: handle GLSL_SAMPLER_DIM_SUBPASS_MS case

Fixes a warning.

Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>

src/gallium/auxiliary/nir/tgsi_to_nir.c

@@ -1341,6 +1341,7 @@ ttn_tex(struct ttn_compile *c, nir_alu_dest dest, nir_ssa_def **src)
       instr->coord_components = 3;
       break;
    case GLSL_SAMPLER_DIM_SUBPASS:
+   case GLSL_SAMPLER_DIM_SUBPASS_MS:
       unreachable("invalid sampler_dim");
    }