can: mcp251xfd: mcp251xfd_irq(): stop timestamping worker in case error in IRQ

In case an error occurred in the IRQ handler, the chip status is
dumped via devcoredump and all IRQs are disabled, but the chip stays
powered for further analysis.

The chip is in an undefined state and will not receive any CAN frames,
so shut down the timestamping worker, which reads the TBC register
regularly, too. This avoids any CRC read error messages if there is a
communication problem with the chip.

Fixes: efd8d98d

 ("can: mcp251xfd: add HW timestamp infrastructure")
Link: https://lore.kernel.org/r/20210724155131.471303-1-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>