Bluetooth: MGMT: Uninitialized variable in load_conn_param()

The "update" variable needs to be initialized to false.

Fixes: 0ece498c ("Bluetooth: MGMT: Make MGMT_OP_LOAD_CONN_PARAM update existing connection")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>