[AGP] intel_agp: extra stolen mem size available for IGD_GM chipset

This adds missing stolen memory size detect for IGD_GM, be sure to
detect right size as current X intel driver (2.3.2) which has already
worked out.

Signed-off-by: Zhenyu Wang <zhenyu.z.wang@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/char/agp/intel-agp.c

@@ -567,13 +567,13 @@ static void intel_i830_init_gtt_entries(void)
 				gtt_entries = 0;
 			break;
 		case G33_GMCH_GMS_STOLEN_128M:
-			if (IS_G33)
+			if (IS_G33 || IS_I965)
 				gtt_entries = MB(128) - KB(size);
 			else
 				gtt_entries = 0;
 			break;
 		case G33_GMCH_GMS_STOLEN_256M:
-			if (IS_G33)
+			if (IS_G33 || IS_I965)
 				gtt_entries = MB(256) - KB(size);
 			else
 				gtt_entries = 0;