DRM: Armada: Add Armada DRM driver

This patch adds support for the pair of LCD controllers on the Marvell
Armada 510 SoCs.  This driver supports:
- multiple contiguous scanout buffers for video and graphics
- shm backed cacheable buffer objects for X pixmaps for Vivante GPU
  acceleration
- dual lcd0 and lcd1 crt operation
- video overlay on each LCD crt via DRM planes
- page flipping of the main scanout buffers
- DRM prime for buffer export/import

This driver is trivial to extend to other Armada SoCs.

Included in this commit is the core driver with no output support; output
support is platform and encoder driver dependent.

Tested-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/gpu/drm/armada/Kconfig

@@ -0,0 +1,15 @@
+config DRM_ARMADA
+	tristate "DRM support for Marvell Armada SoCs"
+	depends on DRM && HAVE_CLK
+	select FB_CFB_FILLRECT
+	select FB_CFB_COPYAREA
+	select FB_CFB_IMAGEBLIT
+	select DRM_KMS_HELPER
+	help
+	  Support the "LCD" controllers found on the Marvell Armada 510
+	  devices.  There are two controllers on the device, each controller
+	  supports graphics and video overlays.
+
+	  This driver provides no built-in acceleration; acceleration is
+	  performed by other IP found on the SoC.  This driver provides
+	  kernel mode setting and buffer management to userspace.