drm: export the DRM permission check code

This way drm_ioctl_permit() can be used by drivers

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>

diff --cc drivers/gpu/drm/drm_ioctl.c
Simple merge

diff --cc include/drm/drmP.h
Simple merge