bayleybay_fsp: Switch from EHCI controller to XHCI

- Disable the EHCI controller and enable the XHCI controller.

SeaBIOS has been tested on the board and boots an OS from a
flashdrive at SuperSpeed.
This also enables the top USB port on the 2-port stack, which goes
through a High Speed Inter-Chip port.  The HSIC port is only enabled
through the XHCI device.

Change-Id: Ic3dfc55028fa5e081a30819fe9596b1a9f57fd9c
Signed-off-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-on: http://review.coreboot.org/6106
Reviewed-by: Dave Frodin <dave.frodin@se-eng.com>
Tested-by: build bot (Jenkins)