iio: magnetometer: ak8975: Fix the error handling in ak8975_power_on()

When the driver fails to enable the regulator 'vid', we will get the
following splat:

[   79.955610] WARNING: CPU: 5 PID: 441 at drivers/regulator/core.c:2257 _regulator_put+0x3ec/0x4e0
[   79.959641] RIP: 0010:_regulator_put+0x3ec/0x4e0
[   79.967570] Call Trace:
[   79.967773]  <TASK>
[   79.967951]  regulator_put+0x1f/0x30
[   79.968254]  devres_release_group+0x319/0x3d0
[   79.968608]  i2c_device_probe+0x766/0x940

Fix this by disabling the 'vdd' regulator when failing to enable 'vid'
regulator.

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Link: https://lore.kernel.org/r/20220409034849.3717231-2-zheyuma97@gmail.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>