batman-adv: Remove kernel fixed width types in packet.h

The uapi headers use the __u8/__u16/... version of the fixed width types
instead of u8/u16/... The use of the latter must be avoided before
packet.h is copied to include/uapi/linux/.

Signed-off-by: Sven Eckelmann <sven.eckelmann@openmesh.com>
Signed-off-by: David S. Miller <davem@davemloft.net>