imx-drm: imx-drm-core: make imx_drm_crtc_register() safer

imx_drm_crtc_register() doesn't clean up the CRTC upon failure, which
leaves the CRTC attached to the DRM device.  Also, it does setup after
attaching the CRTC to the DRM device.

Fix this by reordering the function such that we do the setup before
drm_crtc_init(): this fixes both issues.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>