Bluetooth: Add support for Start Limited Discovery command

This patch implements the mgmt Start Limited Discovery command. Most
of existing Start Discovery code is reused since the only difference
is the presence of a 'limited' flag as part of the discovery state.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/mgmt.h

@@ -584,6 +584,8 @@ struct mgmt_rp_get_adv_size_info {
 	__u8	max_scan_rsp_len;
 } __packed;
 
+#define MGMT_OP_START_LIMITED_DISCOVERY	0x0041
+
 #define MGMT_EV_CMD_COMPLETE		0x0001
 struct mgmt_ev_cmd_complete {
 	__le16	opcode;