acpidump: improve length calculation for several IVHD elements

Use sizeofs of structures corresponding to the parsed device entry.
This does not change the calculation, but fixes logical inconsistency.

Sponsored by:	The FreeBSD Foundation
Sponsored by:	Advanced Micro Devices (AMD)
MFC after:	1 week

usr.sbin/acpi/acpidump/acpi.c

@@ -1629,8 +1629,8 @@ acpi_handle_ivrs_ivhd_devs(ACPI_IVRS_DE_HEADER *d, char *de)
 		} else if (d->Type == ACPI_IVRS_TYPE_EXT_START) {
 			d8b = (ACPI_IVRS_DEVICE8B *)db;
 			len = sizeof(*d8b);
-			d4 = (ACPI_IVRS_DEVICE4 *)(db + sizeof(*d8a));
-			len = sizeof(*d8a) + sizeof(*d4);
+			d4 = (ACPI_IVRS_DEVICE4 *)(db + sizeof(*d8b));
+			len = sizeof(*d8b) + sizeof(*d4);
 			printf("\t\tDev Type=%#x Id=%#06x-%#06x",
 			    d8a->Header.Type, d8a->Header.Id, d4->Header.Id);
 			acpi_handle_ivrs_ivhd_dte(d8b->Header.DataSetting);