[PATCH] AArch64: Remove EMAG ifuncs

[Wilco Dijkstra]

Hi Adhemerval,

> I am not sure how common is the Ampere eMAG, but even though what the real gain
> about dropping these specific routines?  They do not really add much maintainance
> (besides adding some extra runtime on string tests).

It's that time again for my yearly spring cleanup. A few years ago we removed Falkor and 
ThunderX ifuncs. EMAG is from the same era (2018), though its microarchitecture is based
on the X-Gene which was first announced in 2011...

As you can see it's quite a lot of code, and at least for memchr the generic version was
significantly improved and should give equivalent performance. However someone needs
to do that kind of benchmarking regularly so that we use the latest optimized ifuncs rather
than one that was written many years ago and never touched since. This is hard as older
machines get retired.

So in general I want to move away from having lots of different CPU-specific ifuncs and
just provide ifuncs for major architecture features. I've had requests for more SVE ifuncs
given all recent cores support SVE2.

Cheers,
Wilco