nimble/controller: Add helper to check if controller is busy
nimble/controller: Add helper to check if controller is busy

In couple of places we were checking if controller is scanning, advertising
or connection is in progress. Lets make a helper for this

X-Original-Commit: 0536012adbda8df58e2e1f7d548abb626012a2d1

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble