usb: ehci-omap: Make Kconfig select PHY if USB_EHCI_OMAP

The USB_EHCI_OMAP driver currently has a series of Kconfig options
which let users specify a GPIO for the reset pin.  Some devices
may have only one reset, while others might have more.

Since there is a nop phy driver, let's selct enable the PHY
system, and imply the nop phy driver.  The nop phy driver can now
toggle the reset pins when putting the phy in and out of reset.

If the gpio is listed under the phy, it will get toggled and
the hard-coded config options specifying the GPIO numbers can
eventually go away.

Signed-off-by: Adam Ford <aford173@gmail.com>