ipq40xx: add support for Linksys WHW01 v1

ipq40xx: add support for Linksys WHW01 v1

This patch adds support for Linksys WHW01 v1 ("Velop") [FCC ID Q87-03331].

Specification
-------------

SOC:             Qualcomm IPQ4018
WiFi 1:          Qualcomm QCA4019 IEEE 802.11b/g/n
WiFi 2:          Qualcomm QCA4019 IEEE 802.11a/n/ac
Bluetooth:       Qualcomm CSR8811 (A12U)
Ethernet:        Qualcomm QCA8072 (2-port)
SPI Flash 1:     Mactronix MX25L1605D (2MB)
SPI Flash 2:     Winbond W25M02GV (256MB)
DRAM:            Nanya NT5CC128M16IP-DI (256MB)
LED Controller:  NXP PCA963x (I2C)
Buttons:         Single reset button (GPIO).

Notes
-----

There does not appear to be a way to trigger TFTP recovery without entering
U-Boot. The device must be opened to access the serial console in order to
first flash OpenWrt onto a device from factory.

The device has automatic recovery backed by a second set of partitions on
the larger of the two SPI flash ICs. Both the primary and secondary must
be flashed to prevent accidental rollback to "factory" after 3 failed boot
attempts.

Serial console
--------------

A serial console is available on the following pins of the populated J2
connector on the device mainboard (115200 8n1).

(<-- Top of PCB / Device)

  J2
  [o o o o o o]
       |   | |
       |   |  `-- GND
       |    `---- TX
       `--------- RX

Installation instructions
-------------------------

1. Setup TFTP server with server IP set to 192.168.1.236.
2. Copy compiled `...squashfs-factory.bin` to `nodes-jr.img` in tftp root.
3. Connect to console using pinout detailed in the serial console section.
4. Power on device and press enter when prompted to drop into U-Boot.
5. Flash first partition device via `run flashimg`.
6. Once complete, reset device and allow to power up completely.
7. Once comfortable with device upgrade reboot and drop back into U-Boot.
8. Flash the second partition (recovery) via `run flashimg2`.

Revert to "factory"
-------------------

1. Download latest firmware update from vendor support site.
2. Copy extracted `.img` file to `nodes-jr.img` in tftp root.
3. Connect to console using pinout detailed in the serial console section.
4. Power on device and press enter when prompted to drop into U-Boot.
5. Flash first partition device via `run flashimg`.
6. Once complete, reset device and allow to power up completely.
7. Once comfortable with device upgrade reboot and drop back into U-Boot.
8. Flash the second partition (recovery) via `run flashimg2`.

Link: https://github.com/openwrt/openwrt/pull/3682
Signed-off-by: Peter Adkins <peter@sunkenlab.com>
(calibration from nvmem, updated to 5.10+5.15)
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>