qmi_wwan: Add support for Quectel EP06

The Quectel EP06 is a Cat. 6 LTE modem. It uses the same interface as
the EC20/EC25 for QMI, and requires the same "set DTR"-quirk to work.

Signed-off-by: Kristian Evensen <kristian.evensen@gmail.com>
Acked-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>