dm: core: ofnode: Add ofnode_read_bootscript_address()

dm: core: ofnode: Add ofnode_read_bootscript_address()

ofnode_read_bootscript_address() reads bootscript address from
/options/u-boot DT node. bootscr-address or bootscr-ram-offset properties
are read and values are filled. bootscr-address has higher priority than
bootscr-ram-offset and the only one should be described in DT.

Also add test to cover this new function.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/23be3838502efef61803c90ef6e8b32bbd6ede41.1693465140.git.michal.simek@amd.com