Bluetooth: Keep msec in DISCOV_LE_TIMEOUT

To be consistent, lets use msec for this timeout as well.

Note: This define value is a minimum scan time taken from BT Core spec 4.0,
Vol 3, Part C, chapter 9.2.6

Signed-off-by: Lukasz Rymanowski <lukasz.rymanowski@tieto.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>