scsi: ufs: Export ufshcd_uic_change_pwr_mode()

Export ufshcd_uic_change_pwr_mode() to allow vendors to use it for
SoC-specific power mode change design limitations.

Link: https://lore.kernel.org/r/20220616053725.5681-2-stanley.chu@mediatek.com
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>