ath6kl: Set background scan period.

After connect command, send scan params WMI command to
set background scan period. If period value is zero
send 0xffff as bg scan period to disable bg scan.
Set default bg scan period to be 60 seconds if
not specified.

This patch depends on below patch
cfg80211: Add background scan period attribute.

kvalo: fix open parenthesis alignment

Signed-off-by: Bala Shanmugam <bkamatch@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>