Bluetooth: validate retained LE Set CIG Parameters command length

hci_cc_le_set_cig_params() validates the controller response but not the
parameters of the previously sent command.  A short command can claim a
large num_cis without containing the corresponding cis[] array.  A
complete successful response then makes the handler read beyond the
command skb while looking up each CIS ID.

KASAN reports:

  BUG: KASAN: slab-out-of-bounds in hci_cc_le_set_cig_params
  Read of size 1
  hci_cc_le_set_cig_params
  hci_cmd_complete_evt
  hci_event_packet

Obtain the retained parameter length and require both the fixed header and
the complete CIS array before using the command data.

The reproducer no longer triggers a KASAN report with this change.

Fixes: 71e9588435c3 ("Bluetooth: ISO: use correct CIS order in Set CIG Parameters event")
Closes: https://lore.kernel.org/linux-bluetooth/179317463153.87610.8996555110609321376@stu.pku.edu.cn/
Signed-off-by: Yifan Zhang <yfzhang23@stu.pku.edu.cn>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>