Previously, the PCI bus scan was skipping bus 0xFF. Now it does not.
I used a match expression to make sure that all cases are accounted for.

I also changed the PCI dev scan and PCI func scan to use a match
expression in a similar way to make sure all cases are account. While
this is functionally the same as before, the match expression will not
allow unhandled cases and should be easier to read and make it harder
to introduce bugs.

Signed-off-by: Wren Turkal <wt@penguintechs.org>