Merge https://gitlab.denx.de/u-boot/custodians/u-boot-usb

cmd/ab_select.c

common/usb_kbd.c

configs/sandbox64_defconfig

configs/sandbox_defconfig

disk/part.c

doc/android/fastboot-protocol.rst

doc/android/fastboot.rst

doc/board/sipeed/maix.rst

doc/usage/index.rst

doc/usage/partitions.rst

drivers/fastboot/Kconfig

drivers/fastboot/fb_command.c

drivers/fastboot/fb_mmc.c

drivers/mmc/sandbox_mmc.c

drivers/usb/gadget/dwc2_udc_otg.c

drivers/usb/gadget/f_fastboot.c

include/fastboot.h

include/part.h

test/dm/Makefile

test/dm/fastboot.c