Revert "mptcp: handle fastopen disconnect correctly"

This reverts commit 73e268b4 which is
commit 619af16b upstream.

It breaks the Android kernel build and can be brought back in the future
in an safe way if it is really needed.

Bug: 161946584
Change-Id: Ice4a456e51817eb48fad85c2ae048a88338807ef
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>