This reverts commit 17f7ae16.

The commit brought a new socket state LLCP_DISCONNECTING, which was
never set, only read, so socket could never set to such state.

Remove the dead code.
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>