can: move SPI drivers into a separate directory

Create a directory for all CAN drivers using SPI and move mcp251x driver there.

Signed-off-by: Stefano Babic <sbabic@denx.de>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --cc drivers/net/can/Kconfig
Simple merge

diff --cc drivers/net/can/Makefile
Simple merge

diff --cc drivers/net/can/spi/Kconfig
Simple merge

diff --cc drivers/net/can/spi/Makefile
Simple merge

diff --cc drivers/net/can/spi/mcp251x.c
Simple merge