scsi: ufs: Remove redundant vops NULL check and trivial wrapper

ufshcd_variant_hba_init/exit() check 'if (!hba->vops)' before calling
vops wrappers, but the wrappers already do NULL check internally. Remove
the redundant checks. Also remove ufshcd_variant_hba_exit() entirely
since it only wraps ufshcd_vops_exit() with no added value.

Signed-off-by: Chanwoo Lee <cw9316.lee@samsung.com>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/20260529061623.301291-1-cw9316.lee@samsung.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>