dt-bindings: cache: Convert marvell,{feroceon,kirkwood}-cache to DT schema

Convert the Marvell Feroceon/Kirkwood Cache binding to DT schema format.

Use "marvell,kirkwood-cache" for the filename instead as that's only
compatible used in a .dts upstream.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>