ipq806x: add support for Linksys e8350-v1

ipq806x: add support for Linksys e8350-v1

AC2400 Dual-Band Gigabit Wi-Fi Router base on ipq8064.
https://www.linksys.com/support-product?sku=E8350

Specification:
 - Qualcomm dual-core IPQ8064 @ 1.4 GHz
 - 512 MB of RAM
 - 4 MB of SPI NOR MX25U3235F
 - 128 MB of NAND S34MS01G2
 - Qualcomm QCA9880 2.4GHz 802.11bgn
 - Quantenna QSR1000 5GHz 802.11ac (no support)
 - 4 x 10/100/1000 Mbit/s w/ vlan support Ethernet
 - Qualcomm Atheros QCA8337 switch
 - 1 x 3.0 + 1 x 2.0 (combo with eSata port)
 - 115200, 8N1 internal serial console
 - Power, Reset, WPS and WLAN buttons
 - Power, WPS and WLAN leds
 - 12 VDC, 3 A power

Installation:
The installation must be done using web interface of the router.
To achive this new firmware-utils tool was added to set correct
magic headers for the factory images.

Installation from vendor firmware:
 1. Flash over the native Linksys WEB interface using factory image.

Installation using recovery mode:
 1. Power off the device and disconnect the WAN port.
    (Only LAN port to be connected)
 2. Press & hold the "Reset" button
 3. Power on the device & wait 10 seconds with pressed "Reset" button
 4. Set IP Internet Protocol on your PC from
    192.168.1.0/24 network (Router is on IP 192.168.1.1)
 5. Open the Firmware Recovery page in your browser:
    http://192.168.1.1/index.shtml
    Firmware Recovery -> File Name -> Recovery & Reboot

The device page in inbox:
https://openwrt.org/inbox/toh/linksys/linksys_ea8350_1

Signed-off-by: Sergey Filippov <sergey.filippov@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/15798
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>