power: supply: smb5-iio: Add missing braces in smb5_iio_get_prop()

Cross-checked with msm-5.15 tag. The change does not exist as a separate
commit and is squashed into the initial import.

Change-Id: I8ba245606f8b538c9bf3dbdc9dfb621fea721de8
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>