uml: fix initrd printk

If the initrd file has zero-length, the error message should contain
the filepath.

Cc: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: NJohann Felix Soden <johfel@users.sourceforge.net>
Signed-off-by: NJeff Dike <jdike@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/um/kernel/initrd.c

@@ -32,7 +32,7 @@ static int __init read_initrd(void)
 	 * ask for no memory.
 	 */
 	if (size == 0) {
-		printk(KERN_ERR "\"%\" is a zero-size initrd\n");
+		printk(KERN_ERR "\"%s\" is a zero-size initrd\n", initrd);
 		return 0;
 	}