panfrost: Get rid of pan_drm.c

panfrost: Get rid of pan_drm.c

pan_drm.c was only meaningful when we were supporting 2 kernel drivers
(mali_kbase, and the drm one). Now that there's now kernel-driver
abstraction we're better off moving those functions were they belong:

* BO related functions in pan_bo.c
* fence related functions + query_gpu_version() in pan_screen.c
* submit related functions in pan_job.c

While at it, we rename the functions according to the place they're
being moved to.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>