uboot-envtools: ath79: add support for the Buffalo BHR-4GRV2

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>

package/boot/uboot-envtools/files/ath79

@@ -16,6 +16,7 @@ case "$board" in
 buffalo,wzr-hp-ag300h)
         ubootenv_add_uci_config "/dev/mtd3" "0x0" "0x10000" "0x10000"
         ;;
+buffalo,bhr-4grv2|\
 glinet,ar300m|\
 ocedo,koala|\
 ocedo,raccoon|\