iio: hid-sensor: fix return of -EINVAL on invalid values in ret or value

[ Upstream commit c894acc7bf400d039bf740420b22f0b71b7fb504 ]

Ensure that when an invalid value in ret or value is found -EINVAL
is returned. A previous commit broke the way the return error is
being returned and instead caused the return code in ret to be
re-assigned rather than be returned.

Fixes: 5d9854eaea776 ("iio: hid-sensor: Store restore poll and hysteresis on S3")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>