constify a bunch of struct file_operations instances

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/s390/cio/qdio_debug.c b/drivers/s390/cio/qdio_debug.c
index ccaae9d..4221b02 100644
--- a/drivers/s390/cio/qdio_debug.c
+++ b/drivers/s390/cio/qdio_debug.c
@@ -224,7 +224,7 @@
 			   file_inode(filp)->i_private);
 }
 
-static struct file_operations debugfs_perf_fops = {
+static const struct file_operations debugfs_perf_fops = {
 	.owner	 = THIS_MODULE,
 	.open	 = qperf_seq_open,
 	.read	 = seq_read,