iio: light: gp2ap002: fix runtime PM leak on read error

In the Linux kernel, the following vulnerability has been resolved: iio: light: gp2ap002: fix runtime PM leak on read error gp2ap002_read_raw() calls pm_runtime_get_sync() before reading the lux value, but if gp2ap002_get_lux() fails, it returns directly. This skips the pm_runtime_put_autosuspend() call at the "out" label, permanently leaking a runtime PM reference and preventing the device from autosuspending. Replace the direct return with a "goto out" to ensure the reference is properly dropped on the error path.