iio:light:stk3310: adjust indentation

Adjust some indentation issues as spotted by checkpatch.pl --strict

Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
Reviewed-by: Tiberiu Breana <tiberiu.a.breana@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>