Bluetooth: mgmt: Fix wrong opcode in the response for add_adv cmd

This patch fixes the MGMT add_advertising command repsones with the
wrong opcode when it is trying to return the not supported error.

Fixes: cbbdfa6f ("Bluetooth: Enable controller RPA resolution using Experimental feature")
Signed-off-by: Tedd Ho-Jeong An <tedd.an@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>