iio:light:stk3310: adjust indentation

Adjust some indentation issues as spotted by checkpatch.pl --strict
Signed-off-by: NHartmut Knaack <knaack.h@gmx.de>
Reviewed-by: NTiberiu Breana <tiberiu.a.breana@intel.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>