packet: fill the gap of TPACKET_ALIGNMENT with zeros

struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
Explicitly defining and zeroing the gap of this makes additional changes
easier.

Signed-off-by: Atzm Watanabe <atzm@stratosphere.co.jp>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h
index 1e24aa7..9185dc9 100644
--- a/include/uapi/linux/if_packet.h
+++ b/include/uapi/linux/if_packet.h
@@ -133,7 +133,7 @@
 	__u32		tp_sec;
 	__u32		tp_nsec;
 	__u16		tp_vlan_tci;
-	__u16		tp_padding;
+	__u8		tp_padding[6];
 };
 
 struct tpacket_hdr_variant1 {
@@ -154,6 +154,7 @@
 	union {
 		struct tpacket_hdr_variant1 hv1;
 	};
+	__u8		tp_padding[12];
 };
 
 struct tpacket_bd_ts {