intel-iommu: Fix 32-bit build warning with __cmpxchg()

drivers/pci/intel-iommu.c: In function 'dma_pte_addr':
drivers/pci/intel-iommu.c:239: warning: passing argument 1 of '__cmpxchg64' from incompatible pointer type

It seems that __cmpxchg64() now cares about the type of its pointer argument,
so give it a (uint64_t *) instead of a pointer to a structure which contains
only that.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/pci/intel-iommu.c

@@ -236,7 +236,7 @@ static inline u64 dma_pte_addr(struct dma_pte *pte)
 	return pte->val & VTD_PAGE_MASK;
 #else
 	/* Must have a full atomic 64-bit read */
-	return  __cmpxchg64(pte, 0ULL, 0ULL) & VTD_PAGE_MASK;
+	return  __cmpxchg64(&pte->val, 0ULL, 0ULL) & VTD_PAGE_MASK;
 #endif
 }