ipq40xx: add support for ALFA Network AP120C-AC

ipq40xx: add support for ALFA Network AP120C-AC

ALFA Network AP120C-AC is a dual-band ceiling AP, based on Qualcomm
IPQ4018 + QCA8075 platform.

Specification:

- Qualcomm IPQ4018 (717 MHz)
- 256 MB of RAM (DDR3)
- 16 MB (SPI NOR) + 128 MB (SPI NAND) of flash
- 2x Gbps Ethernet, with 802.3af PoE support in one port
- 2T2R 2.4/5 GHz (IPQ4018), with ext. FEMs (QFE1952, QFE1922)
- 3x U.FL connectors
- 1x 1.8 dBi (Bluetooth) and 2x 3/5 dBi dual-band (Wi-Fi) antennas
- Atmel/Microchip AT97SC3205T TPM module (I2C bus)
- TI CC2540 Bluetooth LE module (USB 2.0 bus)
- 4x LED (all driven by GPIO)
- 1x button (reset)
- 1x USB 2.0 (optional, not installed in indoor version)
- DC jack for main power input (12 V)
- UART header available on PCB (2.0 mm pitch)

Flash instruction:

1. This board uses dual-image feature (128 MB NAND is divided into two
   64 MB partitions: 'rootfs1' and 'rootfs2').
2. Before update, make sure your device is running firmware no older
   than v1.1 (previous versions have incompatible U-Boot).
3. Use 'factory' image in vendor GUI or for sysupgrade tool, without
   preserving settings.

Signed-off-by: Piotr Dymacz <pepe2k@gmail.com>