usb: hcd: Remove USB phy if needed

This adds remove_phy flag to the HCD structure. If the flag is
set and if hcd->phy is valid, the phy is shutdown and released
whenever usb_add_hcd fails or usb_hcd_remove is called.
This can be used by the HCD drivers to auto-remove
the external USB phy when it is no longer needed.

Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>