ARM: ux500: Add SDI (MMC) support to the HREF Device Tree

Here we add the Device Tree nodes which are required to successfully
probe the MMCI driver which will enable the four cards available on
ST-Ericsson's HREF hardware development platform.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>