scsi: ufs: exynos: Constify driver data

Constify the drv data because it should not be modified (used by multiple
devices).

Link: https://lore.kernel.org/r/20220613101429.114449-1-krzysztof.kozlowski@linaro.org


Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>