ARM: am335x: Add phyCORE AM335x R2 support

Support for Phytech phyCORE AM335x R2 SOM (PCL060) on the Phytec
phyBOARD-Wega AM335x.

CPU  : AM335X-GP rev 2.1
Model: Phytec AM335x phyBOARD-WEGA
DRAM:  256 MiB
NAND:  256 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 37624b58542f ("Linux 5.1-rc7")

Signed-off-by: Niel Fourie <lusus@denx.de>
Signed-off-by: Parthiban Nallathambi <pn@denx.de>
Reviewed-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
Tested-by: Marek Vasut <marex@denx.de>