A probe function should have a clean return 0 path.

Cc: Cliff Cai <cliff.cai@analog.com>
Signed-off-by: NMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: NBryan Wu <cooloney@kernel.org>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>