ARM: dts: imx7-colibri: add MCP2515 CAN controller

The Colibri Evaluation Carrier Board provides a MCP2515 CAN
controller connected via SPI. Note that the i.MX 7 provides
an internal CAN controller which is much better suited for CAN
operations. Using the MCP2515 with a Colibri iMX7 module is
mainly useful to test the SPI interface.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>