MAINTAINERS: Add reviewer entry for microchip mcp25xxfd SPI-CAN network driver

This patch adds Thomas Kopp as a reviewer for the mcp25xxfd CAN driver.

Signed-off-by: Thomas Kopp <thomas.kopp@microchip.com>
Link: https://lore.kernel.org/r/20200916101334.1277-1-thomas.kopp@microchip.com
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>