gigaset: accept connection establishment messages in any order

commit bceb0f126f25184eaec3f3c8f00c92b0d899e5de upstream.

ISDN connection setup failed if the "connection active" and
"B channel up" messages from the device arrived in a different
order than expected. Modify the state machine to accept them in
any order.

Impact: bugfix

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>