dt-bindings: phy-mtk-tphy: add the properties about address mapping

Add three required properties about the address mapping, including
'#address-cells', '#size-cells' and 'ranges'

Signed-off-by: Chunfeng Yun <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Kishon Vijay Abraham I <[e-mail]>

Documentation/devicetree/bindings/phy/phy-mtk-tphy.txt

···
 		  make use of "mediatek,generic-tphy-v1" on mt2701 instead and
 		  "mediatek,generic-tphy-v2" on mt2712 instead.
 
+- #address-cells:	the number of cells used to represent physical
+		base addresses.
+- #size-cells:	the number of cells used to represent the size of an address.
+- ranges:	the address mapping relationship to the parent, defined with
+		- empty value: if optional 'reg' is used.
+		- non-empty value: if optional 'reg' is not used. should set
+			the child's base address to 0, the physical address
+			within parent's address space, and the length of
+			the address map.
+
 Required nodes	: a sub-node is required for each port the controller
 		  provides. Address range information including the usual
 		  'reg' property is used inside these nodes to describe