According to https://github.com/openwrt/openwrt/pull/1527, support
for the Buffalo BHR-4GRV2 in ath79 requires repartitioning from
an initramfs image, make this easier by supporting uboot-envtools
support out of the box.
Build tested, but not runtime tested.
Signed-off-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>