iwlwifi: scan: create function for scan scheduling params

In the next patch, this code will be used from different places.
As preparation export this code into function.

Signed-off-by: Tova Mussai <tova.mussai@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>