ARM: dts: Add support for phyCORE-AM335x PCM-953 carrier board

The phyCORE-AM335x development kit is a combination of the
phyCORE-AM335x SoM and a PCM-953 carrier board. The features
of the PCM-953 are:
* ETH phy on carrier board: 1x RGMII
* 1x CAN
* Up to 4x UART
* USB0 (otg)
* USB1 (host)
* SD slot
* User gpio-keys
* User LEDs

Signed-off-by: Teresa Remmet <t.remmet@phytec.de>
Reviewed-by: Wadim Egorov <w.egorov@phytec.de>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>