ixgbe: Store VXLAN port number in network order

The VXLAN port number should be stored in network order instead of in host
order as it is accessed from the hot-path in ATR.  This way we can avoid
having to do any byte swaps in order to validate the port number.

I moved the vxlan_port value into a hole in the read-mostly region of the
adapter struct.  This way it should be in a warm cache-line instead of in
some isolated region in memory when it needs to be accessed.

In addition I went through and stripped a bunch of unneeded ifdef flags
since having an extra variable present doesn't really hurt anything and
makes the code easier to read.  I also went through and dropped the
NETIF_F_RXCSUM flag which was being set in hw_encap_features but provides
no value as the flag is not evaluated in the Rx path.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>