ARM: dts: Add devicetree for Storlink/Storm SL93512R

The Storlink Gemini324 EV-Board also known as Storm
Semiconductor SL93512R_BRD is ground zero for the Gemini
devices. We add a device tree so we can support it, it
turns out to be pretty trivial.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>