Docs: dt: Be explicit and consistent in reference to IOMMU specifiers

The generic IOMMU binding says that the meaning of an 'IOMMU specifier'
is defined by the binding of a specific SMMU. The ARM SMMU binding
never explicitly uses the term 'specifier' at all. Update implicit
references to use the explicit term.

In the iommu-map binding change references to iommu-specifier to
"IOMMU specifier" so we are 100% consistent everywhere with terminology
and capitalization.

Signed-off-by: Stuart Yoder <[e-mail]>
Acked-by: Mark Rutland <[e-mail]>
Signed-off-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/iommu/arm,smmu.txt

···
                   combined interrupt, it must be listed multiple times.
 
 - #iommu-cells  : See Documentation/devicetree/bindings/iommu/iommu.txt
-                  for details. With a value of 1, each "iommus" entry
+                  for details. With a value of 1, each IOMMU specifier
                   represents a distinct stream ID emitted by that device
                   into the relevant SMMU.
 
                   SMMUs with stream matching support and complex masters
-                  may use a value of 2, where the second cell represents
-                  an SMR mask to combine with the ID in the first cell.
-                  Care must be taken to ensure the set of matched IDs
-                  does not result in conflicts.
+                  may use a value of 2, where the second cell of the
+                  IOMMU specifier represents an SMR mask to combine with
+                  the ID in the first cell.  Care must be taken to ensure
+                  the set of matched IDs does not result in conflicts.
 
 ** System MMU optional properties:
 

Documentation/devicetree/bindings/pci/pci-iommu.txt

···
 Optional properties
 -------------------
 
-- iommu-map: Maps a Requester ID to an IOMMU and associated iommu-specifier
+- iommu-map: Maps a Requester ID to an IOMMU and associated IOMMU specifier
   data.
 
   The property is an arbitrary number of tuples of
   (rid-base,iommu,iommu-base,length).
 
   Any RID r in the interval [rid-base, rid-base + length) is associated with
-  the listed IOMMU, with the iommu-specifier (r - rid-base + iommu-base).
+  the listed IOMMU, with the IOMMU specifier (r - rid-base + iommu-base).
 
 - iommu-map-mask: A mask to be applied to each Requester ID prior to being
-  mapped to an iommu-specifier per the iommu-map property.
+  mapped to an IOMMU specifier per the iommu-map property.
 
 
 Example (1)