uml: PATH_MAX needs limits.h

Include limits.h to get a definition of PATH_MAX.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/os-Linux/helper.c

@@ -7,6 +7,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <sched.h>
+#include <linux/limits.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
 #include "kern_constants.h"