staging: vchiq_arm: Improve inline documentation

staging: vchiq_arm: Improve inline documentation

Add more comments to the VCHIQ driver, which provides some
high-level descriptions how things work.

Link: https://github.com/raspberrypi/linux/pull/6801
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
[wahrenst@gmx.net: Rewrite commit log]
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
Link: https://patch.msgid.link/20251029-vchiq-destage-v3-3-da8d6c83c2c5@ideasonboard.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>