ramips: improve Samsung CY-SWR1100 support

ramips: improve Samsung CY-SWR1100 support

This patch does the following:

- rename "devdata" flash partition and make it read-only
- switch from gpio-keys-polled to gpio-keys
- add missing power LED
- set correct PCI ID to compatible string in wifi node
- remove ralink,5ghz property in wifi node
- provide label MAC address

Rename devdata partition to devconf as indicated in the stock firmware
partition table:
00030000-00040000: "devdata"
00040000-00050000: "devconf"

Power LED can be controlled by SoC GPIO. Add it in the dts leds node.

RT3092L supports only bgn mode, so it is unnecessary to disable 5GHz band.

Signed-off-by: Sungbo Eo <mans0n@gorani.run>