common: add fdt_simplefb_enable_and_mem_rsv function

Add a new function to activate an existing simple frame buffer node
and add the associated reserved memory, with no-map properties.

This device tree update is only done when the video device is active
and the video buffer is used.

This patch uses '#if CONFIG_IS_ENABLED(DM_VIDEO)' because
gd->video_bottom and gd->video_top are only defined when CONFIG_DM_VIDEO
is activated.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/include/fdt_simplefb.h b/include/fdt_simplefb.h
index 7e54723..41cd740 100644
--- a/include/fdt_simplefb.h
+++ b/include/fdt_simplefb.h
@@ -10,4 +10,5 @@
 #define _FDT_SIMPLEFB_H_
 int fdt_simplefb_add_node(void *blob);
 int fdt_simplefb_enable_existing_node(void *blob);
+int fdt_simplefb_enable_and_mem_rsv(void *blob);
 #endif