iio: light: cm36651: redundant assignment to variable ret

Variable ret is being assigned a value that is never read and
is being re-assigned a little later on. The assignment is redundant
and hence can be removed.

Addresses-Coverity: ("Ununsed value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>