ARM: defconfig: Enable the PL111 DRM driver on vexpress

This updates the Versatile defconfig to use the new P111 DRM
driver that is merged in the DRM subsystem.

We deactivate the old CLCD driver and activate the Pl111 DRM
driver and the SiI9022 HDMI bridge.

We activate DMA memory allocation using CMA so that the special
graphics memory for the on-board CLCD can be used.

Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Tested-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>