qtnfmac: drop unnecessary TLVs from scan command

Most part of scan command data is always present, so no need
to keep it in TLV. Simplify scan command processing moving
most part of its parameters into a fixed part of
qlink_cmd_scan message.

Use fixed dwell time values for normal scan when device is not
connected, and allow wireless card decide on dwell times by
itself if it's operating as a STA and is connected. When
connected, card can select dwell times dynamically based on
traffic conditions to get best results.

Signed-off-by: Igor Mitsyanko <igor.mitsyanko.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>