ARM: ux500: Setup correct settling time for the MMCI regulator

The GPIO controlled MMCI regulator used on the ux5x0 boards takes
100us to settle. There's already a binding to provide such
information. Let's make use of it.
Signed-off-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>

arch/arm/boot/dts/dbx5x0.dtsi

@@ -679,6 +679,7 @@
 			regulator-name = "mmci-reg";
 			regulator-type = "voltage";
 
+			startup-delay-us = <100>;
 			enable-active-high;
 
 			states = <1800000 0x1