ARM: ux500: 8500: define SDI sleep states

This defines the sleep states for the SDI (MMC/SD) interfaces
on the MOP500 reference designs.

Signed-off-by: Patrice Chotard <patrice.chotard@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>