irqchip/renesas-irqc: Add r8a7795 INTC-EX DT documentation

For some reason the name of the external interrupt controller
has changed name with r8a7795, so use "intc-ex" instead of "irqc"
as r8a7795 compat string to follow the friendly documentation.

Signed-off-by: Magnus Damm <[e-mail]>
Reviewed-by: [e-mail]
Acked-by: Geert Uytterhoeven <[e-mail]>
Cc: [e-mail]
Cc: Magnus Damm <[e-mail]>
Link: http://lkml.kernel.org/r/20150928094228.32552.83336.sendpatchset@little-apple
Signed-off-by: Thomas Gleixner <[e-mail]>

Documentation/devicetree/bindings/interrupt-controller/renesas,irqc.txt

···
     - "renesas,irqc-r8a7792" (R-Car V2H)
     - "renesas,irqc-r8a7793" (R-Car M2-N)
     - "renesas,irqc-r8a7794" (R-Car E2)
+    - "renesas,intc-ex-r8a7795" (R-Car H3)
 - #interrupt-cells: has to be <2>: an interrupt index and flags, as defined in
   interrupts.txt in this directory
 - clocks: Must contain a reference to the functional clock.