The previous workaround stopped the preboot phase from loading USB
support, which makes it impossible to use a USB keyboard to select a
generation from the boot menu without using a serial console.
* gnu/packages/patches/u-boot-rockchip-inno-usb.patch: New File.
* gnu/local.mk (dist_patch_DATA): Add patch.
* gnu/packages/bootloaders.scm (%u-boot-rockchip-inno-usb-patch): New variable.
(u-boot)[source]: Add patch.
(u-boot-rockpro64-rk3399, u-boot-pinebook-pro-rk3399): Remove obsolete phase.
