ARM: at91: add basic support for new SoC family lan966

This patch introduces Microchip LAN966 ARMv7 based SoC family
of multiport gigabit AVB/TSN-capable ethernet switches.
It supports two SKUs: 4-port LAN9662 with multiprotocol
processing support and 8-port LAN9668 switch.

LAN966 family includes copper and serial ethernet interfaces,
peripheral interfaces such as PCIe, USB, TWI, SPI, UART, QSPI,
SD/eMMC, Parallel Interface (PI) as well as synchronization
and trigger inputs/outputs.

Signed-off-by: Kavyasree Kotagiri <kavyasree.kotagiri@microchip.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
[nicolas.ferre@microchip.com: merged patches for this SoC introduction]
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20210831102138.2476-1-kavyasree.kotagiri@microchip.com
Link: https://lore.kernel.org/r/20211004105926.5696-5-kavyasree.kotagiri@microchip.com