[s390] remove pointless assignment of ->f_op in vmlogrdr ->open()

The only way we can get to that function is from misc_open(), after
the latter has set file->f_op to exactly the same value we are
(re)assigning there.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/s390/char/vmlogrdr.c

@@ -338,7 +338,6 @@ static int vmlogrdr_open (struct inode *inode, struct file *filp)
 
 	/* set the file options */
 	filp->private_data = logptr;
-	filp->f_op = &vmlogrdr_fops;
 
 	/* start recording for this service*/
 	if (logptr->autorecording) {