samples: can: build with mcp2515 driver
samples: can: build with mcp2515 driver

Add a test config using the mcp2515 sheild to samples/drivers/can so we
catch build issues.

Signed-off-by: Fabio Baltieri <161d407f4dc681bfd4aedb33b8273b2aafd727bc@gmail.com>

zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr