[NETFILTER]: x_tables: make xt_compat_match_from_user usable in iterator macros

Make xt_compat_match_from_user return an int to make it usable in the
*tables iterator macros and kill a now unnecessary wrapper function.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>