staging: vchiq_core: Add comments to remote event parts

struct remote_event and the related functions remote_event_*() provides
a higher function between ARM core and VPU. It's very helpful for a
reviewer to have explaining comments about these parts.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/20221222141553.138563-1-stefan.wahren@i2se.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>