If the ERTM SREJ list is properly allocated but the retransmit list
allocation fails, the SREJ list must be freed before returning from
l2cap_ertm_init.  l2cap_chan_del will not clean up the SREJ list
if l2cap_ertm_init returns a failure code.
Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>