arm64: dts: qcom: msm8916: Pull down PDM GPIOs during sleep

The original qcom kernel changed the PDM GPIOs to be pull-down
during sleep at some point. Reportedly this was done because
there was some "leakage at PDM outputs during sleep":

  https://source.codeaurora.org/quic/la/kernel/msm-3.10/commit/?id=0f87e08c1cd3e6484a6f7fb3e74e37340bdcdee0

I cannot say how effective this is, but everything seems to work
fine with this change so let's apply the same to mainline just
to be sure.

Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Link: https://lore.kernel.org/r/20200605185916.318494-3-stephan@gerhold.netSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

arch/arm64/boot/dts/qcom/msm8916-pins.dtsi

@@ -569,7 +569,7 @@ pinconf {
 				pins = "gpio63", "gpio64", "gpio65", "gpio66",
 				       "gpio67", "gpio68";
 				drive-strength = <2>;
-				bias-disable;
+				bias-pull-down;
 			};
 		};
 	};