qmi_wwan: apply SET_DTR quirk to Sierra WP7607

The 1199:68C0 USB ID is reused by Sierra WP7607 which requires the DTR
quirk to be detected. Apply QMI_QUIRK_SET_DTR unconditionally as
already done for other IDs shared between different devices.

Signed-off-by: Beniamino Galvani <bgalvani@redhat.com>
Acked-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>