All mt7622 devices except for the UBI-variant of the mt7622-rfb1 carry
metadata appended to the sysupgrade image.
Add it for the mt7622-rfb1-ubi as well and check it on sysupgrade to
avoid accidentally flashing firmware for the wrong device (or variant
or future DEVICE_COMPAT_VERSION).
Signed-off-by: Daniel Golle <daniel@makrotopia.org>