wifi: wfx: introduce hif_scan_uniq()

Like hof_scan(), hif_scan_uniq() invoke HIF_SCAN. However, it only
allows to probe one channel and disable probe requests. It works very
well to implement Remain-On-Channel.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231004172843.195332-5-jerome.pouiller@silabs.com