bcm53xx: image: switch Netgear and Buffalo devices to UBI

We still don't have a smart sysupgrade method, but at least we can use
UBI which provides some protection for rootfs (SquashFS).

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42941 3c298f89-4303-0410-b956-a3cf2f4a3e73