qualcommax: ipq60xx: add Qihoo 360V6 support

qualcommax: ipq60xx: add Qihoo 360V6 support

Specifications:
  SoC:     Qualcomm IPQ6000 1.5GHz
  RAM:     NTCC256M16ER-EK 512MiB
  Flash:   W29N01HZSINA 128MiB
  ETH:     QCA8075 (3x LAN, 1x WAN)
  WLAN1:   2.4GHz 802.11b/g/n/ax 2x2
  WLAN2:   5GHz 802.11a/n/ac/ax 2x2
  Power:   DC 12V 1.5A
  Button:  Reset, Wps
  USB:     1x 2.0

Flash instructions:
  1. Download the initramfs image, rename it to
     initramfs.itb, host it with the tftp server.
  2. Interrupt U-Boot and run these commands:
     tftpboot initramfs.itb
     bootm
  3. After openwrt boots up, use scp or luci web
     to upload sysupgrade.bin to upgrade.

Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Link: https://github.com/openwrt/openwrt/pull/15940
Signed-off-by: Robert Marko <robimarko@gmail.com>