ehci-msm: Remove global struct usb_phy variable

Use struct usb_hcd::phy to hold USB PHY instance.

Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Acked-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>