drm/pancsf: WIP for user space submission

This extends the ABI to allow submission of jobs directly from user
space. The ring buffer, doorbell page and CQS syncobj pages are made
available for mapping by user space. A 'kick' ioctl is provided to
request that the command stream is scheduled onto the GPU.

The kernel submission interface is currently still in place, but the
intention is that it should be removed to avoid having to maintain both
ABIs. Because of this, very little thought has gone into ensuring that
the user space submission doesn't undermine the kernel submission
interface.

Signed-off-by: Steven Price <steven.price@arm.com>