Steven Price authored Jun 25, 2021 and Boris Brezillon committed Jun 25, 2021

The hardware has a set of '_NEXT' registers that can hold a second job
while the first is executing. Make use of these registers to enqueue a
second job per slot.

v3:
* Fix the done/err job dequeuing logic to get a valid active state
* Only enable the second slot on GPUs supporting jobchain disambiguation
* Split interrupt handling in sub-functions

Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>