arm64: dts: imx8mq-librem5: Reduce usdhc2's post-power-on-delay-ms to 20ms
This appears to be enough for both Redpine and SparkLAN cards. Waiting for too long makes us waste time in resume from system suspend, so let's keep it as short as possible.
Signed-off-by: Sebastian Krzyszkowiak sebastian.krzyszkowiak@puri.sm