staging:iio:light:tsl2x7x: fix the error handling in tsl2x7x_probe()

Fix to return -EINVAL in the i2c device found error handling
case instead of 0, as done elsewhere in this function.
And also correct the fail1 and fail2 lable to do the right thing.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>