usb: split code locating ACPI companion into port and device

In preparation for handling embedded USB devices let's split
usb_acpi_find_companion() into usb_acpi_find_companion_for_device() and
usb_acpi_find_companion_for_port().

Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Rajat Jain <rajatja@google.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Sukumar Ghorai <sukumar.ghorai@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>