arm64: dts: hikey: Give wifi some time after power-on

commit 83b94417 upstream.

Somewhere along recent changes to power control of the wl1835, power-on
became very unreliable on the hikey, failing like this:

wl1271_sdio: probe of mmc2:0001:1 failed with error -16
wl1271_sdio: probe of mmc2:0001:2 failed with error -16

After playing with some dt parameters and comparing to other users of
this chip, it turned out we need some power-on delay to make things
stable again. In contrast to those other users which define 200 ms, the
hikey would already be happy with 1 ms. Still, we use the safer 10 ms,
like on the Ultra96.

Fixes: ea452678 ("arm64: dts: hikey: Fix WiFi support")
Cc: <stable@vger.kernel.org> #4.12+
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts

@@ -118,6 +118,7 @@ wl1835_pwrseq: wl1835-pwrseq {
 		reset-gpios = <&gpio0 5 GPIO_ACTIVE_LOW>;
 		clocks = <&pmic>;
 		clock-names = "ext_clock";
+		post-power-on-delay-ms = <10>;
 		power-off-delay-us = <10>;
 	};