usb: ehci-mx6: move phy setup before register access

For the CONFIG_PHY case, move the PHY setup before the register access.

This avoids a hang when updating the imx8mm.dtsi which moves the
USB OTG power-domains to the PHY.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Tested-by: Fabio Estevam <festevam@denx.de>