nimble/host: Don't use slave timer with extended advertising
nimble/host: Don't use slave timer with extended advertising

This timer is needed for legacy advertising only. Extended advertising
allows to handle this in controller.

X-Original-Commit: 05899acb7634e3b3ada57f7a8df3273699954b55

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