Updates the u-boot on the Librem 5 to a branch that is much closer to
mainline u-boot.
- adds support for booting from SD card to the u-boot boot script
- m4 is no longer necessary, at least not right now (may be re-added by
purism in the future for supporting some low power modes)
- adds a patch to enable u-boot console on uart 4 (on the m.2 connector)
for the debug board
- drops the patch to enable efidebug command, this isn't necessary
anymore with mainline u-boot
Co-authored-by: Bart Ribbers <bribbers@disroot.org>
2f78939f94