[IA64] compilation fix of iommu.h

Trivial compilation fix of iommu.h.
It includes asm/msi.h for struct msi_desc and struct msi_msg
definition.
msi.h doesn't exist yet on ia64 so declare struct msi_desc and
struct msi_msg in iommu.h and don't include asm/msi.h.
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>

xen/include/xen/iommu.h

@@ -26,7 +26,6 @@
 #include <xen/pci.h>
 #include <public/hvm/ioreq.h>
 #include <public/domctl.h>
-#include <asm/msi.h>
 
 extern int vtd_enabled;
 extern int iommu_enabled;
@@ -79,6 +78,9 @@ int pt_irq_destroy_bind_vtd(struct domain *d,
 unsigned int io_apic_read_remap_rte(unsigned int apic, unsigned int reg);
 void io_apic_write_remap_rte(unsigned int apic,
                              unsigned int reg, unsigned int value);
+
+struct msi_desc;
+struct msi_msg;
 void msi_msg_read_remap_rte(struct msi_desc *msi_desc, struct msi_msg *msg);
 void msi_msg_write_remap_rte(struct msi_desc *msi_desc, struct msi_msg *msg);
 struct qi_ctrl *iommu_qi_ctrl(struct iommu *iommu);