staging: vt6656: lock changes: RXvMngWorkItem.

Narrow atomic locks in RXvMngWorkItem.

We must lock the DequeueRCB and RXvFreeRCB so that
they are in sync.

vMgrRxManagePacket can nolonger be atomically called.

There is no need for an overall lock.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>