omap: IOMMU: add missing function declaration

Declaration of exported function 'iopgtable_lookup_entry' is missing from
header file. Currently we have a sparse warning as it's not being used
externally. Adding its declaration to avoid such warning and allow its usage
in future.
Signed-off-by: David Cohen <dacohen@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/include/plat/iommu.h

@@ -154,6 +154,8 @@ extern void flush_iotlb_range(struct iommu *obj, u32 start, u32 end);
 extern void flush_iotlb_all(struct iommu *obj);
 
 extern int iopgtable_store_entry(struct iommu *obj, struct iotlb_entry *e);
+extern void iopgtable_lookup_entry(struct iommu *obj, u32 da, u32 **ppgd,
+				   u32 **ppte);
 extern size_t iopgtable_clear_entry(struct iommu *obj, u32 iova);
 
 extern int iommu_set_da_range(struct iommu *obj, u32 start, u32 end);