x86/pkeys: Fix pkeys build breakage for some non-x86 arches

Guenter Roeck reported breakage on the h8300 and c6x architectures (among
others) caused by the new memory protection keys syscalls.  This patch does
what Arnd suggested and adds them to kernel/sys_ni.c.

Fixes: a60f7b69 ("generic syscalls: Wire up memory protection keys syscalls")
Reported-and-tested-by: NGuenter Roeck <linux@roeck-us.net>
Signed-off-by: NDave Hansen <dave.hansen@intel.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Cc: linux-arch@vger.kernel.org
Cc: Dave Hansen <dave@sr71.net>
Cc: linux-api@vger.kernel.org
Link: http://lkml.kernel.org/r/20160912203842.48E7AC50@viggo.jf.intel.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

kernel/sys_ni.c

@@ -250,3 +250,8 @@ cond_syscall(sys_execveat);
 
 /* membarrier */
 cond_syscall(sys_membarrier);
+
+/* memory protection keys */
+cond_syscall(sys_pkey_mprotect);
+cond_syscall(sys_pkey_alloc);
+cond_syscall(sys_pkey_free);