scsi: ufs: Remove an outdated comment

scsi: ufs: Remove an outdated comment

Although the host lock had to be held by ufshcd_clk_scaling_start_busy()
callers when that function was introduced, that is no longer the case
today. Hence remove the comment that claims that callers of this function
must hold the host lock.

Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20221018202958.1902564-5-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>