btdev: Add support for LE Set Privacy mode

btdev: Add support for LE Set Privacy mode

This adds support for LE Set Privacy mode which is required when using
Device Privacy mode:

< HCI Command: LE Set Priva.. (0x08|0x004e) plen 8
        Peer Identity address type: Public (0x00)
        Peer Identity address: BC:9A:78:56:34:12 (OUI BC-9A-78)
        Privacy Mode: Use Device Privacy (0x01)
> HCI Event: Command Complete (0x0e) plen 4
      LE Set Privacy Mode (0x08|0x004e) ncmd 1

Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>