mfd: arizona: Signedness bug in arizona_runtime_suspend()

The "jd_active" variable needs to be signed for the error handling to
work.

Fixes: 143e5887ae57 ('mfd: arizona: factor out checking of jack detection state')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>