We can use 'pcimem_start' instead of
introducing 'mtrr_base'. Perhaps, we
should also add a check that the value of 'pcimem_start' is one of:
Oops, the mtrr_base assignment got lost in the whole rebasing process.
That wasn't intentional.
Given that pcimem_start and mtrr_base have the same value for both piix4
and q35 we could drop one indeed.