drm/komeda: Add support for 'memory-region' DT node property

The 'memory-region' property of the komeda display driver DT binding
allows the use of a 'reserved-memory' node for buffer allocations. Add
the requisite of_reserved_mem_device_{init,release} calls to actually
make use of the memory if present.

Changes since v1:
 - Move handling inside komeda_parse_dt
Signed-off-by: Mihail Atanassov <mihail.atanassov@arm.com>
Reviewed-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
Signed-off-by: james qian wang (Arm Technology China) <james.qian.wang@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190805095408.21285-1-mihail.atanassov@arm.com

drivers/gpu/drm/arm/display/komeda/komeda_dev.c

@@ -8,6 +8,7 @@
 #include <linux/iommu.h>
 #include <linux/of_device.h>
 #include <linux/of_graph.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
 #ifdef CONFIG_DEBUG_FS
@@ -143,6 +144,12 @@ static int komeda_parse_dt(struct device *dev, struct komeda_dev *mdev)
 		return mdev->irq;
 	}
 
+	/* Get the optional framebuffer memory resource */
+	ret = of_reserved_mem_device_init(dev);
+	if (ret && ret != -ENODEV)
+		return ret;
+	ret = 0;
+
 	for_each_available_child_of_node(np, child) {
 		if (of_node_cmp(child->name, "pipeline") == 0) {
 			ret = komeda_parse_pipe_dt(mdev, child);
@@ -289,6 +296,8 @@ void komeda_dev_destroy(struct komeda_dev *mdev)
 
 	mdev->n_pipelines = 0;
 
+	of_reserved_mem_device_release(dev);
+
 	if (funcs && funcs->cleanup)
 		funcs->cleanup(mdev);