staging: mmal-vchiq: Fix incorrect static vchiq_instance.

staging: mmal-vchiq: Fix incorrect static vchiq_instance.

For some reason lost in history function vchiq_mmal_init used
a static variable for storing the vchiq_instance.
This value is retrieved from vchiq per instance, so worked fine
until you try to call vchiq_mmal_init multiple times concurrently
when things then go wrong. This seemed to happen quite frequently
if using the cutdown firmware (no MMAL or VCSM services running)
as the vchiq_connect then failed, and one or other vchiq_shutdown
was working on an invalid handle.

Remove the static so that each caller gets a unique vchiq_instance.

Fixes: 7b3ad5abf027 ("staging: Import the BCM2835 MMAL-based V4L2 camera driver.")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Link: https://lore.kernel.org/r/1621979857-26754-1-git-send-email-stefan.wahren@i2se.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>