xen: missing includes

Changes in v2:
- remove pvclock hack;
- remove include linux/types.h from xen/interface/xen.h.
v3:
- Compile under IA64
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 0bfc1ef..1d0d95e 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -47,6 +47,7 @@
 #include <xen/interface/memory.h>
 #include <xen/hvc-console.h>
 #include <asm/xen/hypercall.h>
+#include <asm/xen/interface.h>
 
 #include <asm/pgtable.h>
 #include <asm/sync_bitops.h>