acpi: Bump FADT to revision 6

Some of the revision 4 FADT fields were already updated to ACPI
spec revision 6, but not all of them. In addition the advertised
FADT revision was 3.

Implement all fields as defined in version 6 and bump the advertised
FADT revision to 6.

Also set all used access_size fields and x_gpe0_blk to sane values
as Windows 10 verifies those fields starting with FADT revision 5.

Fixes: https://ticket.coreboot.org/issues/109

Tested on Windows 10.

Change-Id: Ic649040025cd09ed3e490a521439ca4e681afbbf
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39805
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
diff --git a/src/arch/x86/acpi.c b/src/arch/x86/acpi.c
index 6eded1d..a5c5c49 100644
--- a/src/arch/x86/acpi.c
+++ b/src/arch/x86/acpi.c
@@ -1554,7 +1554,7 @@
 {
 	switch (table) {
 	case FADT:
-		return ACPI_FADT_REV_ACPI_3_0;
+		return ACPI_FADT_REV_ACPI_6_0;
 	case MADT: /* ACPI 3.0: 2, ACPI 4.0/5.0: 3, ACPI 6.2b/6.3: 5 */
 		return 2;
 	case MCFG: