ide: Remove unneeded null pointer check

With bm == NULL, other code in the same function would crash.

This bug was reported by cppcheck:
hw/ide/pci.c:280: error: Possible null pointer dereference: bm

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/ide/pci.c

@@ -267,9 +267,7 @@ static void bmdma_irq(void *opaque, int n, int level)
         return;
     }
 
-    if (bm) {
-        bm->status |= BM_STATUS_INT;
-    }
+    bm->status |= BM_STATUS_INT;
 
     /* trigger the real irq */
     qemu_set_irq(bm->irq, level);