Bluetooth: Host: Update BR L2CAP channel state

In the function bt_l2cap_chan_set_state, BR
channel is treated as LE Chan.
The BR L2CAP channel state is updated
incorrectly.

Add a function bt_l2cap_br_chan_set_state
for BR L2CAP channel. For BR/EDR channel,
call bt_l2cap_br_chan_set_state directly.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>