usb: chipidea: add chipidea revision information

Define ci_get_revision API to know the controller revision
information according to chipidea 1.1a, 2.0a and 2.5a spec.
Besides, add one entry at struct ci_hdrc to indicate revision
information, it can be used for adding different code for
revisions, eg kinds of errata.

Reviewed-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>