nimble/controller: Fix initial conn event scheduling on ext adv
nimble/controller: Fix initial conn event scheduling on ext adv

We schedule packet from the end of AUX_ADV_IND packet (like in legacy
advertising), not from its beginning.

X-Original-Commit: a3513040c792a352a3d0ef1693fb2a687bc218fa

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