netrom: fix api breakage in nr_setsockopt()

This needs to copy an unsigned int from user space instead of a long to
avoid breaking user space with an API change.

I have updated all the integer overflow checks from ULONG to UINT as
well.  This is a slight API change but I do not expect it to affect
anything in real life.

Fixes: 3087a6f3 ("netrom: fix copying in user data in nr_setsockopt")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>