can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN

This patch adds support for the Microchip MCP25xxFD SPI CAN controller family.

Tested-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/r/20200918172536.2074504-4-mkl@pengutronix.de