Remove Grub and replace with mainline u-boot & systemd-boot. The two methods to boot now: - Hold the RE button to boot off of the SD Card - With a blank SPI, boot off of eMMC using the power button SPI needs to be blank as u-boot chainloading is broken Signed-off-by: Rudraksha Gupta <guptarud@gmail.com> Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/9135>