regulator: Fix memory leak in max8998_pmic_probe failure path

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>