[PATCH v3] doc: add removal note for power empty poll API

[Pattan, Reshma]

> -----Original Message-----
> From: Thomas Monjalon <thomas at monjalon.net>
<snip>
> > +Removal Note
> > +------------
> > +
> > +The experimental empty poll APIs will be removed from the library in
> > +a future DPDK release.
> 
> After more thoughts, I think it would be better highlighted if moved at the
> beginning of the section "Empty Poll API".
> It could a note block or a warning.
> 
> Also, could we explain how it is replaced?
> 

The empty poll API will be removed completely,  because dpdk now has power pmd modes i.e. monitor, scale and pause which can be used for power saving over empty poll API.

V4 is sent now.