toshiba_acpi: make one-bit bitfields unsigned

This doesn't change how the code works, but it silences a Sparse
complaint:
drivers/platform/x86/toshiba_acpi.c:121:37: error: dubious one-bit signed bitfield
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/toshiba_acpi.c

@@ -118,10 +118,10 @@ struct toshiba_acpi_dev {
 	int last_key_event;
 	int key_event_valid;
 
-	int illumination_supported:1;
-	int video_supported:1;
-	int fan_supported:1;
-	int system_event_supported:1;
+	unsigned int illumination_supported:1;
+	unsigned int video_supported:1;
+	unsigned int fan_supported:1;
+	unsigned int system_event_supported:1;
 
 	struct mutex mutex;
 };