PM / devfreq: event: testing the wrong variable

There is a typo here so we test "edev" but we intended to test
"edev[i]".

Fixes: f262f28c ('PM / devfreq: event: Add devfreq_event class')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>