[NETFILTER]: Fix compat_xt_counters alignment for non-x86

Some (?) non-x86 architectures require 8byte alignment for u_int64_t
even when compiled for 32bit, using u_int32_t in compat_xt_counters
breaks on these architectures, use u_int64_t for everything but x86.

Reported by Andreas Schwab <schwab@suse.de>.

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