dm: core: Add a new API devfdt_get_addr_index_ptr()

At present there is only devfdt_get_addr_ptr() which only returns
the first <addr, size> pair in the 'reg' property. Add a new API
devfdt_get_addr_index_ptr() to return the indexed pointer.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

include/dm/fdtaddr.h

@@ -92,6 +92,18 @@ void *devfdt_map_physmem(const struct udevice *dev, unsigned long size);
  */
 fdt_addr_t devfdt_get_addr_index(const struct udevice *dev, int index);
 
+/**
+ * devfdt_get_addr_index_ptr() - Return indexed pointer to the address of the
+ *                               reg property of a device
+ *
+ * @dev: Pointer to a device
+ * @index: the 'reg' property can hold a list of <addr, size> pairs
+ *	   and @index is used to select which one is required
+ *
+ * @return Pointer to addr, or NULL if there is no such property
+ */
+void *devfdt_get_addr_index_ptr(const struct udevice *dev, int index);
+
 /**
  * devfdt_get_addr_size_index() - Get the indexed reg property of a device
  *