mISDN: Bugfix for layer2 fixed TEI mode

If a fixed TEI is used, the initial state of the layer 2 statmachine need to be
4 (TEI assigned). This was true only for Point to Point connections, but not
for the other fixed TEIs. It was not found before, because usually only the
TEI 0 is used as fixed TEI for PtP mode, but if you try X31 packet mode
connections with SAPI 16, TEI 1, it did fail.

Signed-off-by: Karsten Keil <keil@b1-systems.de>
Cc: <stable@vger.kernel.org> # 3.5.x
Signed-off-by: David S. Miller <davem@davemloft.net>