mISDN: Fix irq detection

Fix false irq detection on disabled irqs.

Signed-off-by: Andreas Eversberg <andreas@eversberg.eu>
Signed-off-by: Karsten Keil <kkeil@suse.de>
diff --git a/drivers/isdn/hardware/mISDN/hfcmulti.c b/drivers/isdn/hardware/mISDN/hfcmulti.c
index 592db93..4cfab20 100644
--- a/drivers/isdn/hardware/mISDN/hfcmulti.c
+++ b/drivers/isdn/hardware/mISDN/hfcmulti.c
@@ -2658,6 +2658,7 @@
 	if (status & V_MISC_IRQSTA) {
 		/* misc IRQ */
 		r_irq_misc = HFC_inb_nodebug(hc, R_IRQ_MISC);
+		r_irq_misc &= hc->hw.r_irqmsk_misc; /* ignore disabled irqs */
 		if (r_irq_misc & V_STA_IRQ) {
 			if (hc->type == 1) {
 				/* state machine */