ramips: add support for Asus RT-AC65P

ramips: add support for Asus RT-AC65P

The Asus RT-AC65P router is identical with the RT-AC85P, but better to make separate images for it.

On both routers the installation can be done also via SSH:

Note: The user/password for SSH is identical with the one used in the
Web-interface.

1. Complete the initial setup wizard.
2. Activate SSH under "Administration" -> "System".
3. Transfer the OpenWrt factory image via scp:
 > scp openwrt-ramips-mt7621-asus_rt-ac65p-squashfs-factory.bin admin@192.168.50.1:/tmp
4. Connect via SSH to the router.
 > ssh admin@192.168.50.1
5. Write the OpenWrt image to flash.
 > mtd-write -i
/tmp/openwrt-ramips-mt7621-asus_rt-ac65p-squashfs-factory.bin -d linux
6. Reboot the router
 > reboot

Changelog:

v3: removed [] from filename, rebased to latest master
v2: Rebased to latest master
v1: Initial release

Signed-off-by: Gabor Varga <vargagab@gmail.com>