The dev_read_addr_ptr() mimics the behaviour of the devfdt_get_addr_ptr(),
retrieving the first address of the node's reg-property and returning
it as a pointer (or NULL on failure).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>