hp-wmi: fix regressions caused by missing if statement

Error was introduced in commit fe8e4e03

 ("hp-wmi: handle
rfkill_register() failure").

Signed-off-by: Frans Pop <elendil@planet.nl>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Acked-by: Matthew Garrett <mjg@redhat.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>