USB: cdc-acm: restore capability check order

commit b401f8c4 ("USB: cdc-acm: fix rounding error in TIOCSSERIAL")
introduced a regression by changing the order of capability and close
settings change checks. When running with CAP_SYS_ADMIN setting the
close settings to the values already set resulted in -EOPNOTSUPP.

Fix this by changing the check order back to how it was before.

Fixes: b401f8c4 ("USB: cdc-acm: fix rounding error in TIOCSSERIAL")
Cc: Anthony Mallet <anthony.mallet@laas.fr>
Cc: stable <stable@vger.kernel.org>
Cc: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Matthias Reichl <hias@horus.com>
Link: https://lore.kernel.org/r/20200327150350.3657-1-hias@horus.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -923,16 +923,16 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss)
 
 	mutex_lock(&acm->port.mutex);
 
+	if (!capable(CAP_SYS_ADMIN)) {
 		if ((ss->close_delay != old_close_delay) ||
-            (ss->closing_wait != old_closing_wait)) {
-		if (!capable(CAP_SYS_ADMIN))
+		    (ss->closing_wait != old_closing_wait))
 			retval = -EPERM;
-		else {
+		else
+			retval = -EOPNOTSUPP;
+	} else {
 		acm->port.close_delay  = close_delay;
 		acm->port.closing_wait = closing_wait;
 	}
-	} else
-		retval = -EOPNOTSUPP;
 
 	mutex_unlock(&acm->port.mutex);
 	return retval;