ac/nir: Return frag_coord as integer.

To preserve the invariant that nir ssa defs are integers or pointers
in LLVM.

CC: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/amd/common/ac_nir_to_llvm.c

@@ -3232,7 +3232,8 @@ static void visit_intrinsic(struct ac_nir_context *ctx,
 			ctx->abi->frag_pos[2],
 			ac_build_fdiv(&ctx->ac, ctx->ac.f32_1, ctx->abi->frag_pos[3])
 		};
-		result = ac_build_gather_values(&ctx->ac, values, 4);
+		result = ac_to_integer(&ctx->ac,
+		                       ac_build_gather_values(&ctx->ac, values, 4));
 		break;
 	}
 	case nir_intrinsic_load_front_face: