kernel/auditfilter.c: fixing build warning

  kernel/auditfilter.c:426: warning: this decimal constant is unsigned only in ISO C90

Signed-off-by: Raphael S. Carvalho <raphael.scarv@gmail.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>