s390/pci: Deletion of unnecessary checks before the function call "debug_unregister"

The debug_unregister() function performs also input parameter validation.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
Signed-off-by: NSebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/pci/pci_debug.c

@@ -158,10 +158,7 @@ int __init zpci_debug_init(void)
 
 void zpci_debug_exit(void)
 {
-	if (pci_debug_msg_id)
-		debug_unregister(pci_debug_msg_id);
-	if (pci_debug_err_id)
-		debug_unregister(pci_debug_err_id);
-
+	debug_unregister(pci_debug_msg_id);
+	debug_unregister(pci_debug_err_id);
 	debugfs_remove(debugfs_root);
 }