netfilter: fix hardcoded size assumptions

get_random_bytes() is sometimes called with a hard coded size assumption
of an integer. This could not be true for next centuries. This patch
replace it with a compile time statement.

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --cc net/netfilter/nf_conntrack_core.c
Simple merge

diff --cc net/netfilter/nf_conntrack_expect.c
Simple merge

diff --cc net/netfilter/xt_hashlimit.c
Simple merge