ANDROID: GKI: provide more padding for struct usb_phy

There is at least one pending change for struct usb_phy that is not
going to make the ABI freeze deadline, but has already been submitted
upstream and is under active development.  So reserve a spot for that
new callback to be added, and provide a bit more buffer here to the
structure for any future LTS changes that might be coming in this area
of the kernel

Bug: 151154716
Cc: Stanley Chang <stanley_chang@realtek.com>
Change-Id: I992a46fa35502fd491ee24d503290119c9b9f655
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>