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/20231025153455.283c5b12@canb.auug.org.au/
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20231025131854.375388-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

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.