[SeaBIOS] seabios serial console vs. sgabios

[Gerd Hoffmann]

Hi,

One problem we have with the serial console support in seabios and
sgabios:  It can happen that both are activated.  We'll go fix that in
qemu, but that'll work for new qemu versions only, not for the old
already released ones.

So I think it would be useful if seabios makes sure sgabios and serial
console are not both active at the same time, i.e. in case we find
"vgaroms/sgabios.bin" being present either turn off builtin serial
console, or don't load sgabios (and possibly also enable builtin serial
console).

Comments?

cheers,
  Gerd