acer-wmi: does not allow negative number set to initial device state

The driver set module parameter value: mailled, threeg and brightness
to BIOS by evaluate wmi method when driver was initialed. The default
values for those parameters are -1, so, that will be better don't set
negative value to BIOS.

Cc: Carlos Corbacho <carlos@strangeworlds.co.uk>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Lee, Chun-Yi <jlee@novell.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/acer-wmi.c

@@ -961,9 +961,11 @@ static void __init acer_commandline_init(void)
 	 * These will all fail silently if the value given is invalid, or the
 	 * capability isn't available on the given interface
 	 */
+	if (mailled >= 0)
 		set_u32(mailled, ACER_CAP_MAILLED);
-	if (!has_type_aa)
+	if (!has_type_aa && threeg >= 0)
 		set_u32(threeg, ACER_CAP_THREEG);
+	if (brightness >= 0)
 		set_u32(brightness, ACER_CAP_BRIGHTNESS);
 }