P51XX: dock audio: follow your little brother [1/2]

We already use "dock" instead "analog-dock" for P5110 https://github.com/Dhollmen/Dhollmen_vendor/blob/KK_4.4/samsung/p51xx/p5110/system/etc/sound/espresso10wifi#L119

For P31XX we use "dock" - so let's follow our little brother.