OMAP4 support is present but there isn't any board using it. Add minimal support for the Variscite OMAP4-SoM (debug console + boot from SD card). Use the ti/omap/omap4-var-stk-om44 device-tree from the Linux kernel. The real representation of the SoM's hardware is located in ti/omap/omap4-var-som-om44.dtsi included in it. Set myself as maintainer for it. Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>