scsi: ufs: ufs-mediatek: Modify the minimum RX/TX lane count to 2

scsi: ufs: ufs-mediatek: Modify the minimum RX/TX lane count to 2

MediaTek UFS host now supports 2 lanes. Modify the lane count to 2.

This modification shall not impact old 1-lane host because
PA_CONNECTEDRXDATALANES and PA_CONNECTEDTXDATALANES will limit the target
lanes properly during power mode change. So we could relax the limitation
in ufs_dev_params.

Link: https://lore.kernel.org/r/20200819084340.7021-1-stanley.chu@mediatek.com
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Andy Teng <andy.teng@mediatek.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>