rt2800: do VCO calibration after programming ALC

Somehow AP doesn't come up and the first scan fails if we don't do
VCO calibration every time.
The vendor driver duplicates the VCO calibration function into the
channel switching logic, we can do the same with less duplication.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>