can: bcm: switch timer to HRTIMER_MODE_SOFT and remove hrtimer_tasklet

This patch switches the timer to HRTIMER_MODE_SOFT, which executed the
timer callback in softirq context and removes the hrtimer_tasklet.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>