ACPICA: Do not use extended sleep registers unless HW-reduced bit is set

Previous implementation incorrectly used the ACPI 5.0 extended
sleep registers if they were simply populated. This caused
problems on some non-HW-reduced machines. As per the ACPI spec,
they should only be used if the HW-reduced bit is set.  Lv Zheng,
ACPICA BZ 1020.

References: https://bugzilla.kernel.org/show_bug.cgi?id=54181
References: https://bugs.acpica.org/show_bug.cgi?id=1020Reported-by: Daniel Rowe <bart@fathom13.com>
Bisected-by: Brint E. Kriebel <kernel@bekit.net>
Cc: 3.4+ <stable@vger.kernel.org>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/hwxfsleep.c

@@ -240,12 +240,14 @@ static acpi_status acpi_hw_sleep_dispatch(u8 sleep_state, u32 function_id)
 	    &acpi_sleep_dispatch[function_id];
 
 #if (!ACPI_REDUCED_HARDWARE)
-
 	/*
 	 * If the Hardware Reduced flag is set (from the FADT), we must
-	 * use the extended sleep registers
+	 * use the extended sleep registers (FADT). Note: As per the ACPI
+	 * specification, these extended registers are to be used for HW-reduced
+	 * platforms only. They are not general-purpose replacements for the
+	 * legacy PM register sleep support.
 	 */
-	if (acpi_gbl_reduced_hardware || acpi_gbl_FADT.sleep_control.address) {
+	if (acpi_gbl_reduced_hardware) {
 		status = sleep_functions->extended_function(sleep_state);
 	} else {
 		/* Legacy sleep */