The buffer used to transfer data over the mailbox interface is mapped
using the client's device. This is incorrect, as the device performing
the DMA transfer is the mailbox itself. Fix it by using the mailbox
controller device instead.

This requires including the mailbox_controller.h header to dereference
the mbox_chan and mbox_controller structures. The header is not meant to
be included by clients. This could be fixed by extending the client API
with a function to access the controller's device.

Fixes: 4e3d6065 ("ARM: bcm2835: Add the Raspberry Pi firmware driver")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Tested-by: Ivan T. Ivanov <iivanov@suse.de>
Link: https://lore.kernel.org/r/20240326195807.15163-3-laurent.pinchart@ideasonboard.comSigned-off-by: Florian Fainelli <florian.fainelli@broadcom.com>