bcm47xx: add support for NETGEAR R6200 V1

bcm47xx: add support for NETGEAR R6200 V1

This patch adds supports for the NETGEAR R6200 V1
This device is mainlined in Linux as of 5.4

Specification:
   - SOC: Broadcom BCM4718A1 (480 MHz)
   - Flash: 16MB (Macronix MX25L128)
   - RAM: 128MB DDR2
   - SWITCH: BCM53125
   - Ethernet: 5x GE (1 WAN + 4 LAN, Inverted order)
   - WLAN 2.4G: In SOC
   - WLAN 5GHz: miniPCIe card, BCM4352 (ID: 4360)
   - USB: 1x USB 2.0 port (Type A)
   - Buttons: Reset, WLAN, WPS
   - LED: Amber for Power, others need a workaround
   - UART: 1x UART on PCB

LED Issues: They are controlled by a 74HC164 via bit banging(GPIO 6/7)

Firmware Install Instructions
=============================
Using the device specific .chk, use that file to perform
a normal device upgrade in the OEM admin page.

Signed-off-by: Edward Matijevic <motolav@gmail.com>