[IPV4]: annotate inetdev.h helpers

inet_confirm_addr(), inet_ifa_byprefix(), ip_dev_find(), inet_make_mask() and
inet_ifa_match() annotated, along with inferred net-endian variables

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>