Add board code and DTs for Renesas RZ/A1 SoC-based GR-Peach,
which is a cheap development platform with RZ/A1H SoC. The
DTs are imported from Linux 5.0.11, commit d5a2675b207d .

Currently supported are UART, ethernet and RPC SPI. The board
can be booted from RPC SPI by writing the u-boot.bin binary
to the beginning of the SPI NOR, e.g. using the "sf" command.
The board can also be booted via JTAG by setting text base to
0x20020000, loading u-boot.bin there via JTAG and executing it
from that address.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Chris Brandt <chris.brandt@renesas.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>