Add delayed scheduled scan request

Add delayed scheduled scan request

When initializing, the scheduled scan code was being called before
everything is ready. With normal scans, the first scan round is
delayed, so the initialization is finished by the time it really
starts.

Add a function that can be used to request a delayed scheduled scan.
The scan will only start after the specified time has elapsed. Call
this function instead of starting the scheduled scan directly during
driver initialization.

Signed-off-by: Luciano Coelho <coelho@ti.com>