linux-phytec-ti

drm: Extract drm_master_relase

Like with drm_master_open protect it with a check for primary_client
to make it clear that this can't happen on render/control nodes.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465930269-7883-7-git-send-email-daniel.vetter@ffwll.ch