scsi: target: tcmu: Fix warning: 'page' may be used uninitialized

Corrects drivers/target/target_core_user.c:688:6: warning: 'page' may be
used uninitialized.

Link: https://lore.kernel.org/r/20200924001920.43594-1-john.p.donnelly@oracle.com
Fixes: 3c58f73 ("scsi: target: tcmu: Optimize use of flush_dcache_page")
Cc: Mike Christie <michael.christie@oracle.com>
Acked-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: John Donnelly <john.p.donnelly@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/target_core_user.c

@@ -699,7 +699,7 @@ static void scatter_data_area(struct tcmu_dev *udev, struct tcmu_cmd *tcmu_cmd,
 	void *from, *to = NULL;
 	size_t copy_bytes, offset;
 	struct scatterlist *sg;
-	struct page *page;
+	struct page *page = NULL;
 
 	for_each_sg(se_cmd->t_data_sg, sg, se_cmd->t_data_nents, i) {
 		int sg_remaining = sg->length;