usb: chipidea: clarify Documentation/ABI text

Fix grammar and improve readability of chipidea-usb2 text.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Peter Chen <peter.chen@kernel.org>
Cc: linux-usb@vger.kernel.org
Acked-by: Peter Chen <peter.chen@kernel.org>
Link: https://lore.kernel.org/r/20220827203217.7837-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>