ath79: fix firmware partition attributes for GL-AR300M16 and -Lite

ath79: fix firmware partition attributes for GL-AR300M16 and -Lite

During the introduction of the ath79/nand images for the GL-AR300M
series the firmware partition label and compatible were altered,
but the necessary adjustments have not been made for the
GL-AR300M16 and the GL-AR300M-Lite. This will result in a
non-bootable partition setup for these devices.

This patch adds the necessary definitions to those two devices.

Fixes: 55e6c903ae20 ("ath79: GL-AR300M: provide NAND support;
       increase to 4 MB kernel")
Fixes: b591cabd3989 ("ath79: add GL.iNet GL-AR300M16 as NOR-only
       board")

Signed-off-by: Jeff Kletsky <git-commits@allycomm.com>
[extend commit message, alter commit title]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>