MIPS: Add missing definition for MADV_HWPOISON.

Thanks to Joseph S. Myers for reporting this.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: "Joseph S. Myers" <joseph@codesourcery.com>
Patchwork: http://patchwork.linux-mips.org/patch/723/

arch/mips/include/asm/mman.h

@@ -75,6 +75,7 @@
 
 #define MADV_MERGEABLE   12		/* KSM may merge identical pages */
 #define MADV_UNMERGEABLE 13		/* KSM may not merge identical pages */
+#define MADV_HWPOISON    100		/* poison a page for testing */
 
 /* compatibility flags */
 #define MAP_FILE	0