dt-bindings: phy: Add binding for marvell,mmp3-hsic-phy

This is the PHY chip for USB HSIC on MMP3 platform.

Link: https://lore.kernel.org/r/20191220065314.237624-4-lkundrak@v3.sk


Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Olof Johansson <olof@lixom.net>