nimble/controller: Extract function to prepare and send adv report
nimble/controller: Extract function to prepare and send adv report

This patch did minor refactor which will be needed for legacy extended
advertising support

X-Original-Commit: d070d7336e87522b4341049b48c45229e4d8512c

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