iio: tsl4531: fix error handling in tsl4531_check_id()

The tsl4531_check_id() function returned 1 on "found" and 0 on "not
found" and negative error codes on failure.  This was non-standard and
bug prone.  The caller treated all non-zero values including error codes
as "found".

This patch fixes it by changing the tsl4531_check_id() to return zero on
success or a negative error code, and updates the caller.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>