scsi: ufs: Remove redundant null checking of devfreq instance

hba->devfreq is zero-initialized thus it is not required to check its
existence in ufshcd_add_lus() function which is invoked during
initialization only.

Link: https://lore.kernel.org/r/20210120150142.5049-3-stanley.chu@mediatek.com


Reviewed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>