m68knommu: use one exist from execption

Part of the code that did not make sense to me got removed by Greg.
This is part two:

The first compare is to check whether the interrupts are disabled or not.
Depending on the result we exectute the RESTORE_ALL macro is not only
restoring the stack but also returning to caller.
The test for pending softirq has been removed because it is allready done
in irq_exit().
Since system_call() is allso using the SAVE_ALL macro and returning via
ret_from_exception label I see no reason why we could not do this here
as well. This is also handy because if we return from the timer interrupt
and we need to resched than we check for this :)

Signed-off-by: Sebastian Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>