ldattach: always set line speed and format for N_GIGASET_M101

ldattach: always set line speed and format for N_GIGASET_M101

The Gigaset M101 exhibits particularly awkward and confusing behaviour
when the serial line speed isn't set to what the device expects:
Configuration mode detects the used speed and works anyway, but data
mode silently fails. Troubleshooting this is enormously time-consuming.

Spare the users this trouble by setting the line speed and format to
these devices' factory default values as long as the command line
doesn't say otherwise.

Signed-off-by: Tilman Schmidt <tilman@imap.cc>