Staging: pohmelfs: crypto processing.

POHMELFS is able to encrypt the whole network channel or
attach the strong checksum to own packets to catch faulty media.

This patch implements crypto initialization, its autoconfiguration
and sync with the server.

Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>