net: macb: fail when there's no PHY

[Andrew Lunn]

> > > 5.10 is LTS. Well, it will be, once it is actually released!
> > 
> > Convincing people to ship an unreleased kernel would be a whole
> > 'nother bucket of worms.
> 
> +1
> 
> Judging just from the release dates of the last LTS kernels, I would have 
> guessed v5.11 will get LTS.  But there has been no announcement yet and I 
> suppose there will be none before release?

It was announced a while ago. e.g:

https://itsfoss.com/kernel-5-10/

	Andrew