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>
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 955555d..3b5176d 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -225,6 +225,8 @@
 
 source "drivers/gpu/drm/cirrus/Kconfig"
 
+source "drivers/gpu/drm/armada/Kconfig"
+
 source "drivers/gpu/drm/rcar-du/Kconfig"
 
 source "drivers/gpu/drm/shmobile/Kconfig"