drm: imx: imx-hdmi: convert imx-hdmi to drm_bridge mode

drm: imx: imx-hdmi: convert imx-hdmi to drm_bridge mode

IMX6 and Rockchip RK3288 and JZ4780 (Ingenic Xburst/MIPS)
use the interface compatible Designware HDMI IP, but they
also have some lightly differences, such as phy pll configuration,
register width, 4K support, clk useage, and the crtc mux configuration
is also platform specific.

To reuse the imx hdmi driver, convert it to drm_bridge

handle encoder in imx-hdmi_pltfm.c, as most of the encoder
operation are platform specific such as crtc select and
panel format set

This patch depends on Russell King's patch:
 drm: imx: convert imx-drm to use the generic DRM OF helper
 http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2014-July/053484.html

Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>