Revert "iommu/vt-d: Remove unused function"

This reverts commit c61c255.

The pasid_set_wpe() helper, which was removed by the reverted commit,
is still used by the nesting translation support in the iommufd tree.
To avoid a merge conflict, revert the commit.

Link: https://lore.kernel.org/linux-kernel/[email protected]/
Signed-off-by: Lu Baolu <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Joerg Roedel <[email protected]>

Author: LuBaolu

drivers/iommu/intel/pasid.c

@@ -335,6 +335,15 @@ static inline void pasid_set_fault_enable(struct pasid_entry *pe)
 	pasid_set_bits(&pe->val[0], 1 << 1, 0);
 }
 
+/*
+ * Setup the WPE(Write Protect Enable) field (Bit 132) of a
+ * scalable mode PASID entry.
+ */
+static inline void pasid_set_wpe(struct pasid_entry *pe)
+{
+	pasid_set_bits(&pe->val[2], 1 << 4, 1 << 4);
+}
+
 /*
  * Setup the P(Present) field (Bit 0) of a scalable mode PASID
  * entry.