PM / devfreq: passive: fix compiler warning

[ Upstream commit 0465814831a926ce2f83e8f606d067d86745234e ]

The recent commit of
PM / devfreq: passive: Use non-devm notifiers
had incurred compiler warning, "unused variable 'dev'".

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>