Required to allow sysupgrades from OpenWrt 19.07.
Closes#7071
Fixes: 98fbf2edc021 ("ath79: move TPLINK_HWID/_HWREV to parent for tplink-safeloader")
Tested-by: J. Burfeind <git@aiyionpri.me>
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>