i2c0 dtoverlay fixes

[6by9]

Hopefully the commits are self-explanatory.

[pelwell]

I believe that fragment 8 could be replaced with:

        __exports__ {
                i2c0;
        };

Although the exports section was intended to add new symbols to the base DTB, I don't think there's anything to stop it replacing an exsting symbol.

Having said that, your version has a symmetry with the aliases patch, and it's clear that something magic is occuring - an export is perhaps less obvious in that respect.

[6by9]

You're more knowledgeable on DT than me.

Will __exports__ work when i2c0 already exists as a node from the base DT (pointing at soc/i2c0mux/i2c@0)?

[pelwell]

I don't think there's anything to stop it replacing an existing symbol.

[6by9]

Minor annoyance that it seems that sudo dtoverlay i2c0 registers the node as /dev/i2c-11 (or whatever the next unaliased node is), it doesn't get routed to /dev/i2c-0.
Loading from config.txt sends it to /dev/i2c-0.

[6by9]

I don't think there's anything to stop it replacing an existing symbol.

Apologies - missed that line first time around.