net: gro: fix napi_gro_cb zeroed alignment

Add 2 byte padding to napi_gro_cb struct to ensure zeroed member is
aligned after flush_id member was removed in the original commit.

Fixes: 4b0ebbc ("net: gro: move L3 flush checks to tcp_gro_receive and udp_gro_receive_segment")
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Richard Gobert <richardbgobert@gmail.com>
Link: https://lore.kernel.org/r/fca08735-c245-49e5-af72-82900634f144@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/gro.h

@@ -42,8 +42,7 @@ struct napi_gro_cb {
 	/* Used in ipv6_gro_receive() and foo-over-udp and esp-in-udp */
 	u16	proto;
 
-	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
-	__wsum	csum;
+	u16	pad;
 
 /* Used in napi_gro_cb::free */
 #define NAPI_GRO_FREE             1
@@ -85,6 +84,9 @@ struct napi_gro_cb {
 		u8	is_flist:1;
 	);
 
+	/* used to support CHECKSUM_COMPLETE for tunneling protocols */
+	__wsum	csum;
+
 	/* L3 offsets */
 	union {
 		struct {