can: mcp251x: add support for mcp25625

Fully compatible with mcp2515, the mcp25625 have integrated transceiver.

This patch adds support for the mcp25625 to the existing mcp251x driver.

Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>