media: qcom: camss: Fix V4L2 async notifier error path

Previously the jump label err_cleanup was used higher in the probe()
function to release the async notifier however the async notifier
registration was moved later in the code rendering the previous four jumps
redundant.

Rename the label from err_cleanup to err_v4l2_device_unregister to capture
what the jump does.

Fixes: 51397a4ec75d ("media: qcom: Initialise V4L2 async notifier later")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil: fix old name in commit log: err_v4l2_device_register -> err_v4l2_device_unregister]