Meta: Add isa-vga device to ISA-PC and microvm machine types
With this device being added, we can now boot into graphics mode on
these platforms too. For ISA-PC machine this is basically the only
viable option to use, but in the future, we should remove this device
for the microvm machine type as it should allow us to determine better
options and detect them by using a given device tree blob.
Liav A