NFS: Change nfs_find_client() to take "struct sockaddr *"

Adjust arguments and callers of nfs_find_client() to pass a
"struct sockaddr *" instead of "struct sockaddr_in *" to support non-IPv4
addresses.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: Aurelien Charbon <aurelien.charbon@ext.bull.net>

Trond: Also fix up protocol version number argument in nfs_find_client() to
use the correct u32 type.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>