net: rtm_to_ifaddr: free ifa if ifa_cacheinfo processing fails

Commit 5c766d64

 ("ipv4: introduce address lifetime") leaves the ifa
resource that was allocated via inet_alloc_ifa() unfreed when returning
the function with -EINVAL. Thus, free it first via inet_free_ifa().

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Reviewed-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>