MLK-20160-1 usb: ehci-mx6: Fix PHY power up issue on iMX8 platforms

MLK-20160-1 usb: ehci-mx6: Fix PHY power up issue on iMX8 platforms

On iMX8 platforms like 8QM/QXP, we must power up the USB PHY resource
before accessing the PHY. However, current init flow access the USB PHY
in ehci_mx6_common_init prior than ehci_usb_phy_mode where the PHY is power
up.

Fix the issue by adding ehci_get_usb_phy function to parse the PHY address
from DTB and power up the PHY before ehci_mx6_common_init.

Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 477dd3a2cbd73a0ff67cbf15e1e6b7809864b516)