drm: remove master fd restriction on mode setting getters

Its useful to be able to call the mode setting getter ioctls.
Not requiring master fd, enables writing a simple program which
can query the state of the video system.

Since these ioctls are only "getters" there is no security or
synchronization issues which would require master fd. Opening
an new fd is already protected by the file permissions on the
device file.

Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ilija Hadzic <ihadzic@research.bell-labs.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Stephane Marchesin <marcheu@chromium.org>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>