x86: fix ds.c build error

fix:
arch/x86/kernel/ds.c: In function ‘ds_allocate_buffer':
arch/x86/kernel/ds.c:339: error: implicit declaration of function ‘PAGE_ALIGN'

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index 24a323c95997..ab21c270bfa4 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -29,6 +29,7 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
+#include <linux/mm.h>
 
 
 /*