scsi: ufs: core: Simplify ufshcd_auto_hibern8_update()

scsi: ufs: core: Simplify ufshcd_auto_hibern8_update()

Calls to ufshcd_auto_hibern8_update() are already serialized: this function
is either called if user space software is not running (preparing to
suspend) or from a single sysfs store callback function.  Kernfs serializes
sysfs .store() callbacks. No functionality is changed.

Reviewed-by: Bao D. Nguyen <quic_nguyenb@quicinc.com>
Reviewed-by: Can Guo <quic_cang@quicinc.com>
Cc: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20231214192416.3638077-3-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>