ACPI, APEI, GHES, Support disable GHES at boot time

Some machine may have broken firmware so that GHES and firmware first
mode should be disabled.  This patch adds support to that.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>