[PATCH v2] Pioneer devices: engage implicit feedback sync for playback

[Olivia Mackintosh]

> As a blind shot: might the stall be avoided by passing the recently
> introduced chip->playback_first flag?  The revised patch is below.

This appears to fix the issue, thank you! I am curious as to why this is
not required for Geraldo's DDJ-SR2.

My initial thought was that certain devices that restrict capture unless
regular SysEx/Control URBs are sent may mean that Playback first support
is required (e.g. 750, 850, 450). Please correct me if this intuition is
incorrect.

Olivia