ACPI: Schedule /proc/acpi/event for removal

Schedule /proc/acpi/event for removal in 6 months.

Re-name acpi_bus_generate_event() to acpi_bus_generate_proc_event()
to make sure there is no confusion that it is for /proc/acpi/event only.

Add CONFIG_ACPI_PROC_EVENT to allow removal of /proc/acpi/event.
There is no functional change if CONFIG_ACPI_PROC_EVENT=y

Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index 5405813..2e79a33 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -284,7 +284,7 @@
 		}
 		input_sync(input);
 
-		acpi_bus_generate_event(button->device, event,
+		acpi_bus_generate_proc_event(button->device, event,
 					++button->pushed);
 		break;
 	default: