dm: core: implement dev_map_physmem()

This API helps to map physical register addresss pace of device to
virtual address space easily. Its just a wrapper around map_physmem()
with MAP_NOCACHE flag.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Suggested-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jteki@openedev.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jagan Teki <jteki@openedev.com>

include/dm/device.h

@@ -466,6 +466,19 @@ fdt_addr_t dev_get_addr(struct udevice *dev);
  */
 void *dev_get_addr_ptr(struct udevice *dev);
 
+/**
+ * dev_map_physmem() - Read device address from reg property of the
+ *                     device node and map the address into CPU address
+ *                     space.
+ *
+ * @dev: Pointer to device
+ * @size: size of the memory to map
+ *
+ * @return  mapped address, or NULL if the device does not have reg
+ *          property.
+ */
+void *dev_map_physmem(struct udevice *dev, unsigned long size);
+
 /**
  * dev_get_addr_index() - Get the indexed reg property of a device
  *