scsi: ufs-mediatek: Make some symbols static

Fix sparse warnings:

drivers/scsi/ufs/ufs-mediatek.c:19:6: warning: symbol 'ufs_mtk_cfg_unipro_cg' was not declared. Should it be static?
drivers/scsi/ufs/ufs-mediatek.c:55:5: warning: symbol 'ufs_mtk_bind_mphy' was not declared. Should it be static?
drivers/scsi/ufs/ufs-mediatek.c:342:27: warning: symbol 'ufs_mtk_of_match' was not declared. Should it be static?

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>