scsi: ufs: Introduce vops for resetting device

Some UFS memory devices needs their reset line toggled in order to get them
into a good state for initialization. Provide a new vops to allow the
platform driver to implement this operation.

Link: https://lore.kernel.org/r/20190828191756.24312-2-bjorn.andersson@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>