drm/msm: Add per-instance submit queues

Currently the priority and other behavior of a command stream
is provided by the user application during submission and
the application is expected to internally maintain the settings
for each 'context' or 'rendering queue' and specify the correct
ones.

This works okay for simple cases but as applications become more
complex we will want to set context specific flags and do various
permisson checks to allow certain contexts to enable additional
privileges.

Add kernel-side submit queues to be analogous to 'contexts' or
'rendering queues' on the application side. Each file descriptor
instance will maintain its own list of queues. Queues cannot be
shared between file descriptors.

For backwards compatibility context id '0' is defined as a default
context specifying middle priority and no special flags. This is
intended to be the usual configuration for 99% of applications so
that a garden variety application can function correctly without
creating a queue. Only those applications requiring the specific
benefit of different queues need create one.

In addition to the basic infrastructure, allow the user to specify
the queue priority - this will be used in lieu of the legacy
flags to set priority during the submission. Only the master DRM
instance can set the highest priority, but all the others are open
to all processes.

Change-Id: Ic0dedbad02fa27c0ba20c1157a05ddb143e46357
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>