isdn: hisax: Replace the bogus access to irq stats

isdn: hisax: Replace the bogus access to irq stats

commit 40f08a724fcc21285cf3a75aec957aef908605c6 upstream.

Abusing irq stats in a driver for counting interrupts is a horrible
idea and not safe with shared interrupts. Replace it by a local
interrupt counter.

Noticed by the attempt to remove the irq stats export.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Cc: maximilian attems <max@stro.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>