arm64: zynqmp: Add support for Xilinx Kria SOM board

arm64: zynqmp: Add support for Xilinx Kria SOM board

There are couple of revisions of SOMs (k26) and associated carrier cards
(kv260).
SOM itself has two major versions:
sm-k26 - SOM with EMMC
smk-k26 - SOM without EMMC used on starter kit with preprogrammed firmware
in QSPI.

SOMs are describing only devices available on the SOM or connections which
are described in specification (for example UART, fwuen).

When SOM boots out of QSPI it uses limited number of peripherals defined by
the specification and present in sm(k)-k26 dtses.
Then a carrier card (CC) detection is happening and DT overlay is applied
to brings new functionality. That's why DT overlays are used. The name is
composed together with SOM name and CC name that's why DT overlays with
these names are generated to make sure they can be used together.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1ba32590670434b650bacf6410a65579dd30b38b.1632294439.git.michal.simek@xilinx.com