acpi: limit the AMDI0020/AMDI0010 workaround to an option

It appears that production versions of EPYC firmware get the _STA method right
for these nodes. In fact, this workaround breaks on production hardware by
including too many uart nodes. This work around was for pre-release hardware
that wound up not having a large deployment. Move this work around to a kernel
option since the machines that needed it have been powered off and are difficult
to resurrect. Should there be a more significant deployment than is understood,
we can restrict it based on smbios strings.

Discussed with: mmacy@, seanc@, jhb@
MFC After: 3 days