boot: pxe_utils: Add extension board devicetree overlay support
Add support for scanning and applying extension board devicetree
overlays during PXE boot. After loading the main board devicetree,
the system now scans for available extension boards and applies their
overlays automatically.
This enables dynamic hardware configuration for systems with extension
boards during boot scenarios which are using pxe_utils.
Signed-off-by: Kory Maincent (TI.com) <kory.maincent@bootlin.com>
Reviewed-by: Simon Glass <sjg@chromium.org>