drivers: can: mcp2515: Add driver for MCP2515 CAN controller

The MCP2515 is a CAN controller that can be connected via SPI to an
host MCU. This driver adds support for the MCP2515 as a new driver in
the CAN subsystem.
As it is a SPI peripheral it uses a thread for its interrupt
handling and the received message filtering is done inside this
interrupt thread, as the MCP2515 filter capabilities are not sufficient
for the Zephyr CAN interface.
The driver was validated with an external CAN logger and the adjusted
CAN sample application.

Signed-off-by: Karsten Koenig <karsten.koenig.030@gmail.com>