iio: dac: Remove redundant pm_runtime_mark_last_busy() calls

iio: dac: Remove redundant pm_runtime_mark_last_busy() calls

pm_runtime_put_autosuspend(), pm_runtime_put_sync_autosuspend(),
pm_runtime_autosuspend() and pm_request_autosuspend() now include a call
to pm_runtime_mark_last_busy(). Remove the now-redundant explicit call to
pm_runtime_mark_last_busy().

Also clean up error handling in stm32_dac_set_enable_state().

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://patch.msgid.link/20250828140617.3193288-1-sakari.ailus@linux.intel.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>