imx-drm: initialise drm components directly

Now that our bind function is only ever called during the main DRM
driver ->load callback, we don't need to have the imx_drm_connector or
imx_drm_encoder abstractions anymore.  So let's get rid of it, and move
the DRM connector and encoder setup into the connector support files.

Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>