drm/msm: Take the ioctls away from the KMS-only driver

KMS-only drivers should only allocate dumb buffers.  The driver custom
ioctls are only meant for the usermode gpu driver (mesa), and not for
general consumption, so they don't make sense for standalone KMS
drivers.

Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/662598/