phy: marvell: a3700: Set USB3 RX wait depending on ref clock

According to specification, CFG_PM_RXDLOZ_WAIT should be set to 0x7
when reference clock is at 25 MHz. The specification (at least the
version I have) does not mentoin the setting for 40 MHz reference
clock, but Marvell's U-Boot sets 0xC in that case.

Signed-off-by: Marek Behun <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>