msi-wmi: Fix memory leak

Fix memory leak - don't forget to kfree ACPI object when returning from
msi_wmi_notify() after suppressing key event.

Signed-off-by: Maxim Mikityanskiy <maxtram95@gmail.com>
Acked-by: Anisse Astier <anisse@astier.eu>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>