dts/zero-sugar: add 150 us delay for WIFI_PWR_EN

There is a 2 cycles (32K clock) delay required between WIFI_PWR_EN and
WL_REG_ON assertion. Let's use 'startup-delay-us' of WIFI_PWR_EN
regulator to add that delay.  We increase the delay from required 61 us
to 150 us for some margin.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/zero-sugar.dts

@@ -72,6 +72,7 @@
 		pinctrl-0 = <&pinctrl_brcm_reg>;
 		gpio = <&gpio6 13 GPIO_ACTIVE_HIGH>;
 		enable-active-high;
+		startup-delay-us = <150>;
 	};