Bluetooth: Fix fast connectable state when enabling page scan

When powering on or enabling page scan we need to ensure that the page
scan parameters are as they should be. This is because some controllers
do not properly reset these values upon HCI_Reset. Since the
write_scan_parameters function is now called from several new places it
also checks for the >= 1.2 HCI version requirement before sending the
commands.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>