[NETFILTER]: compat offsets size change

Used by compat code offsets of entries should be 'unsigned int' as entries
array size has this dimension.

Signed-off-by: Dmitry Mishin <dim@openvz.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>