MFC r356849: bcm2835_vcbus: unifdef all platform definitions

Raspberry Pi are all over the board, and the reality is that there's no harm
in including all of the definitions by default but plenty of harm in the
current situation. This change is safe because we match a definition by root
/compatible in the FDT, so there will be no false-positives because of it.

The main array of definitions grows, but it's only walked exactly once to
determine which we need to use.