Prepare v2021.10-rc4

Signed-off-by: Tom Rini <trini@konsulko.com>

# gpg: Signature made Tue 14 Sep 2021 06:58:32 PM EDT
# gpg:                using RSA key 1A3C7F70E08FAB1707809BBF147C39FF9634B72C
# gpg: Good signature from "Thomas Rini <trini@konsulko.com>" [ultimate]

# Conflicts:
#	board/Arcturus/ucp1020/spl.c
#	cmd/mvebu/Kconfig
#	common/Kconfig.boot
#	common/image-fit.c
#	configs/UCP1020_defconfig
#	configs/sifive_unmatched_defconfig
#	drivers/pci/Kconfig
#	include/configs/UCP1020.h
#	include/configs/sifive-unmatched.h
#	lib/Makefile
#	scripts/config_whitelist.txt