ARM: dts: imx6qdl: Allow disabling the PU regulator, add a enable ramp delay

The PU regulator is enabled during boot, but not necessarily always-on.
It can be disabled by the generic pm domain framework when the PU power
domain is shut down. The ramp delay of 150 us might be a bit conservative,
the value is taken from the Freescale kernel.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx6qdl.dtsi

@@ -600,7 +600,7 @@ reg_pu: regulator-vddpu@140 {
 					regulator-name = "vddpu";
 					regulator-min-microvolt = <725000>;
 					regulator-max-microvolt = <1450000>;
-					regulator-always-on;
+					regulator-enable-ramp-delay = <150>;
 					anatop-reg-offset = <0x140>;
 					anatop-vol-bit-shift = <9>;
 					anatop-vol-bit-width = <5>;