can: mcp251xfd: add TX IRQ coalescing support

This patch adds TX IRQ coalescing support to the driver.

The implemented algorithm is similar to the RX IRQ coalescing support
added in the previous patch.

Link: https://lore.kernel.org/20220313083640.501791-11-mkl@pengutronix.de


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>