usb: qcserial: define and use Sierra Wireless layout

All the "non Gobi" Qualcomm based devices handled by this
driver share a common standard Sierra Wireless specific
layout. Adding code specifically for this layout allow
us to reduce the number of match entries per device from
three to one.

This change will result in a penalty wrt stable backports,
but simplifies new Sierra device addtitions in the long
term.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>