ARM: dts: vf610-zii-cfu1: Slow I2C0 down to 100 kHz

Fiber-optic modules attached to the bus are only rated to work at
100 kHz, so decrease the bus frequency to accommodate that.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>