scsi: ufs: ufs-exynos: Remove an unnecessary NULL check

The "head" pointer can't be NULL because it points to an address in the
middle of a ufs_hba struct.  Looking at this code, probably someone would
wonder if the intent was to check whether "hba" is NULL, but "hba" isn't
NULL and the check can just be removed.

Link: https://lore.kernel.org/r/20200626105133.GF314359@mwanda


Acked-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>