char: virtio_fastrpc: Add snapshot of virtio fastrpc driver

This snapshot is taken as of dev-sa8155 branch
commit 18dcf6bbb4a9 ("char: virtio_fastrpc: add dma handle support").

Change-Id: I3a918907a319ee397f99162e57644d07504a5dd6
Signed-off-by: Anuj Garg <anujgarg@codeaurora.org>