Bluetooth: hci_sync: fix mesh adv timeout units

Mesh adv instance timeout and duration are in milliseconds, see
mesh_send_sync, hci_add_adv_instance.  hci_schedule_adv_instance_sync()
and hci_enable_ext_advertising_sync() ignore this, and scale the timeout
wrong.

Fix for mesh instances by using msecs_to_jiffies() in
hci_schedule_adv_instance_sync and fixing the scaling in
hci_enable_ext_advertising_sync.

Fixes BlueZ "Mesh - Send cancel" test failures.

Fixes: b338d91703fa ("Bluetooth: Implement support for Mesh")
Assisted-by: opencode:qwen3.8-flash-next sashiko
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>