clk: mvebu: Update binding documentation for the core divider clock

The Core Divider clock support two new compatible strings for Armada
375 and Armada 380 SoCs. Add the compatible strings to the documentation.

Signed-off-by: Ezequiel Garcia <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Jason Cooper <[e-mail]>

Documentation/devicetree/bindings/clock/mvebu-corediv-clock.txt

···
  0 = nand (NAND clock)
 
 Required properties:
-- compatible : must be "marvell,armada-370-corediv-clock"
+- compatible : must be "marvell,armada-370-corediv-clock",
+		       "marvell,armada-375-corediv-clock",
+		       "marvell,armada-380-corediv-clock",
+
 - reg : must be the register address of Core Divider control register
 - #clock-cells : from common clock binding; shall be set to 1
 - clocks : must be set to the parent's phandle