vxlan/geneve: Include udp_tunnel.h in vxlan/geneve.h and fixup includes

This patch makes it so that we add udp_tunnel.h to vxlan.h and geneve.h
header files.  This is useful as I plan to move the generic handlers for
the port offloads into the udp_tunnel header file and leave the vxlan and
geneve headers to be a bit more protocol specific.

I also went through and cleaned out a number of redundant includes that
where in the .h and .c files for these drivers.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>