can: peak_canfd: rearrange the way resources are released

This patch improves the sequence the resources are released by, first,

- disabling the IRQ in the controller, then by
- resetting the DMA logic, and finally, by
- adding a read cycle to ensure that the above commands have been received

before freeing the system interrupt.

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>