devicetree: bindings: R-Car Gen2 CMT0 and CMT1 bindings

Add documentation for new separate CMT0 and CMT1 DT compatible strings
for R-Car Gen2. These compat strings allow us to enable CMT1-specific
features in the driver. The old compat strings will be deprecated in
the not so distant future.

Signed-off-by: Magnus Damm <[e-mail]>
Acked-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Daniel Lezcano <[e-mail]>

Documentation/devicetree/bindings/timer/renesas,cmt.txt

···
 		(CMT1 on sh73a0 and r8a7740)
 		This is a fallback for the above renesas,cmt-48-* entries.
 
+    - "renesas,rcar-gen2-cmt0" for 32-bit CMT0 devices included in R-Car Gen2.
+    - "renesas,rcar-gen2-cmt1" for 48-bit CMT1 devices included in R-Car Gen2.
+
     - "renesas,cmt-48-r8a73a4" for the r8a73a4 48-bit CMT
 		(CMT[01])
     - "renesas,cmt-48-r8a7790" for the r8a7790 48-bit CMT