net: vxget: clean up sparse warnings

This code is copying strings in 64 bit quantities, the device
returns them in big endian. As long as we store in big endian
IOW endian on both sides matches, we're good, so swap to_be64,
not from be64.

This fixes ~60 sparse warnings.

Link: https://lore.kernel.org/r/20201212234426.177015-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>