ramips: fix Archer C20 sysupgrade
The sysupgrade image failed the check due to the wrong string in the
supported devices. This patch provides the correct name by dropping the
SUPPORTED_DEVICES to use the default generated name.
Signed-off-by: Steffen Förster <[email protected]>
[drop the SUPPORTED_DEVICES, the old name was never used in a release]
Signed-off-by: Mathias Kresin <[email protected]>
Steffen Förster