atm: eni: Use tasklet_disable_in_atomic() in the send() callback

The atmdev_ops::send callback which calls tasklet_disable() is invoked with
bottom halfs disabled from net_device_ops::ndo_start_xmit(). All other
invocations of tasklet_disable() in this driver happen in preemptible
context.

Change the send() call to use tasklet_disable_in_atomic() which allows
tasklet_disable() to be made sleepable once the remaining atomic context
usage sites are cleaned up.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210309084242.415583839@linutronix.de