udf: fix udf_debug macro

udf_debug should be enclosed with do { } while (0)
to be safely used in code like below:
if (something)
	udf_debug();
else
	anything;
(Otherwise compiler will not compile it with:
"error: expected expression before 'else'")
Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/udf_fs.h

@@ -39,11 +39,11 @@
 
 #ifdef UDFFS_DEBUG
 #define udf_debug(f, a...) \
-	{ \
+	do { \
 		printk (KERN_DEBUG "UDF-fs DEBUG %s:%d:%s: ", \
 			__FILE__, __LINE__, __FUNCTION__); \
 		printk (f, ##a); \
-	}
+	} while (0)
 #else
 #define udf_debug(f, a...) /**/
 #endif