Add .dts file for rev. C of the board by factoring out commonalities
into a shared include file (vf610-zii-dev-rev-b-c.dtsi) and deriving
revision specific file from it (vf610-zii-dev-rev-b.dts and
vf610-zii-dev-reb-c.dts).

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Stefan Agner <stefan@agner.ch>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: andrew@lunn.ch
Cc: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Cc: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Cc: cphealy@gmail.com
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>