net: bt: Fix warning when compiling without debug

With CONFIG_NET_DEBUG_L2_BLUETOOTH is disabled the code generate the
following warning:

subsys/net/ip/l2/bluetooth.c: In function 'eir_found':
subsys/net/ip/l2/bluetooth.c:301:16: warning: unused variable 'addr' [-Wunused-variable]
  bt_addr_le_t *addr = user_data;
                ^

Change-Id: I1a1ca20c4f2e4fa8aa2a551d2fffa1f86874760e
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>