ACPICA: FADT: Fix extraneous length mismatch warning

Incorrect register length mismatch between the 32 and 64 bit
registers in some cases. Code was was checking the wrong pointer
for non-zero, should be looking at the address within the GAS
structure.
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLin Ming <ming.m.lin@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/acpica/tbfadt.c

@@ -491,7 +491,8 @@ static void acpi_tb_validate_fadt(void)
 		 * For each extended field, check for length mismatch between the
 		 * legacy length field and the corresponding 64-bit X length field.
 		 */
-		if (address64 && (address64->bit_width != ACPI_MUL_8(length))) {
+		if (address64->address &&
+		    (address64->bit_width != ACPI_MUL_8(length))) {
 			ACPI_WARNING((AE_INFO,
 				      "32/64X length mismatch in %s: %d/%d",
 				      name, ACPI_MUL_8(length),