ARM: am335x: Add phyBOARD REGOR support

phyBOARD-REGOR is based on phyCORE AM335x R2 SoM (PCL060).

CPU  : AM335X-GP rev 2.1
Model: Phytec AM335x phyBOARD-REGOR
DRAM:  512 MiB
NAND:  512 MiB
MMC:   OMAP SD/MMC: 0
eth0: ethernet@4a100000

Working:
 - Eth0
 - i2C
 - MMC/SD
 - NAND
 - UART
 - USB (host)

Device trees were taken from Linux mainline:
commit c4d6fe731176 ("Linux 5.9.0")

Signed-off-by: Parthiban Nallathambi <parthiban@linumiz.com>
Reviewed-by: Tom Rini <trini@konsulko.com>