drm: change ioctl permissions

Previously read-only KMS ioctls had some somewhat inconsistent settings
regarding whether mastership was required.  For example, GETRESOURCES
did not require master, but GETPLANERESOURCES, GETPROPERTY, etc. did.

At least for debugging, it is nice to be able to use modetest to dump
property values while another process is master, and there seems to
be no harm in allowing read-only access to the KMS state to other
processes.

Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>