md: Fix apparent cut-and-paste error in super_90_validate

Setting a variable to itself probably wasn't the intention here.
Signed-off-by: NDave Jones <davej@fedoraproject.org>
Signed-off-by: NNeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -1180,7 +1180,7 @@ static int super_90_validate(struct mddev *mddev, struct md_rdev *rdev)
 			mddev->bitmap_info.offset =
 				mddev->bitmap_info.default_offset;
 			mddev->bitmap_info.space =
-				mddev->bitmap_info.space;
+				mddev->bitmap_info.default_space;
 		}
 
 	} else if (mddev->pers == NULL) {