ACPICA: Events: Add runtime stub support for event APIs

ACPICA commit 99bc3beca92c6574ea1d69de42e54f872e6373ce

It is reported that on Linux, RTC driver complains wrong errors on
hardware reduced platform:
  [    4.085420] ACPI Warning: Could not enable fixed event - real_time_clock (4) (20160422/evxface-654)

This patch fixes this by correctly adding runtime reduced hardware check.
Reported by Chandan Tagore, fixed by Lv Zheng.

Link: https://github.com/acpica/acpica/commit/99bc3bec
Tested-by: Chandan Tagore <tagore.chandan@gmail.com>
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/evxfevnt.c

@@ -180,6 +180,12 @@ acpi_status acpi_enable_event(u32 event, u32 flags)
 
 	ACPI_FUNCTION_TRACE(acpi_enable_event);
 
+	/* If Hardware Reduced flag is set, there are no fixed events */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_ACPI_STATUS(AE_OK);
+	}
+
 	/* Decode the Fixed Event */
 
 	if (event > ACPI_EVENT_MAX) {
@@ -237,6 +243,12 @@ acpi_status acpi_disable_event(u32 event, u32 flags)
 
 	ACPI_FUNCTION_TRACE(acpi_disable_event);
 
+	/* If Hardware Reduced flag is set, there are no fixed events */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_ACPI_STATUS(AE_OK);
+	}
+
 	/* Decode the Fixed Event */
 
 	if (event > ACPI_EVENT_MAX) {
@@ -290,6 +302,12 @@ acpi_status acpi_clear_event(u32 event)
 
 	ACPI_FUNCTION_TRACE(acpi_clear_event);
 
+	/* If Hardware Reduced flag is set, there are no fixed events */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_ACPI_STATUS(AE_OK);
+	}
+
 	/* Decode the Fixed Event */
 
 	if (event > ACPI_EVENT_MAX) {