net headers: cleanup dcbnl.h

1) add an include for <linux/types.h>
2) change dcbmsg.dcb_family from unsigned char to __u8 to be more
   consistent with use of kernel types

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>