iio: magnetometer: mag3110: Place driver on standby on error

Place driver on standby mode on error in order to prevent wasting
power. Move standby function above to be seen by the new call.

Signed-off-by: Cristina Opriceana <cristina.opriceana@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>