Bluetooth: Fix not initializing L2CAP tx_credits

Bluetooth: Fix not initializing L2CAP tx_credits

commit ba8f5289f706aed94cc95b15cc5b89e22062f61f upstream.

l2cap_le_flowctl_init was reseting the tx_credits which works only for
outgoing connection since that set the tx_credits on the response, for
incoming connections that was not the case which leaves the channel
without any credits causing it to be suspended.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org # 4.20+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>