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>

arch/ia64/include/asm/xen/interface.h

@@ -265,6 +265,8 @@ typedef struct xen_callback xen_callback_t;
 
 #endif /* !__ASSEMBLY__ */
 
+#include <asm/pvclock-abi.h>
+
 /* Size of the shared_info area (this is not related to page size).  */
 #define XSI_SHIFT			14
 #define XSI_SIZE			(1 << XSI_SHIFT)