Bluetooth: HCI: Fix definition of hci_rp_delete_stored_link_key

num_keys is actually 2 octects not 1:

BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 4, Part E
page 1989:

  Num_Keys_Deleted:
  Size: 2 octets
  0xXXXX	Number of Link Keys Deleted

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>