sanitize const/signedness for udf

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
index 82372e3..b2d96f4 100644
--- a/fs/udf/balloc.c
+++ b/fs/udf/balloc.c
@@ -547,7 +547,7 @@
 		}
 
 		if (epos.offset + (2 * adsize) > sb->s_blocksize) {
-			char *sptr, *dptr;
+			unsigned char *sptr, *dptr;
 			int loffset;
 
 			brelse(oepos.bh);