af_unix: __unix_find_socket_byname() cleanup

Remove pointless return variable dance.

Appears vestigial from when the function did locking as seen in
unix_find_socket_byinode(), but locking is handled in
unix_find_socket_byname() for __unix_find_socket_byname().

Signed-off-by: Vito Caputo <vcaputo@pengaru.com>
Signed-off-by: David S. Miller <davem@davemloft.net>