Revert "USB: qcserial/option: make AT URCs work for Sierra Wireless MC73xx"

This reverts commit d80c0d14
(excluding the change to MAX_BL_NUM, which has since been removed).

The qcserial driver now enables the SET_CONTROL_LINE_STATE request
so that AT URCs will work. Move these devices back to the qcserial
driver, which is used for other devices in this series that follow
the same layout.

Cc: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David Ward <david.ward@ll.mit.edu>
Signed-off-by: Johan Hovold <johan@kernel.org>