scsi: ufs: ufs-exynos: Demote seemingly unintentional kerneldoc header

scsi: ufs: ufs-exynos: Demote seemingly unintentional kerneldoc header

This is the only use of kerneldoc in the source file and no descriptions
are provided.

Fixes the following W=1 kernel build warning(s):

In file included from  drivers/scsi/ufs/ufs-exynos.c:23:
 drivers/scsi/ufs/ufs-exynos.c:234: warning: Function parameter or member 'ufs' not described in 'exynos_ufs_auto_ctrl_hcc'
 drivers/scsi/ufs/ufs-exynos.c:234: warning: Function parameter or member 'en' not described in 'exynos_ufs_auto_ctrl_hcc'

Link: https://lore.kernel.org/r/20200723122446.1329773-7-lee.jones@linaro.org
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Kukjin Kim <kgene@kernel.org>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Seungwon Jeon <essuuj@gmail.com>
Cc: linux-samsung-soc@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>