tty: constify tty_port_operations structs

Constifies tty_port_operations structures in
the tty driver since they are not modified
after their initialization.

Detected and found using Coccinelle.

Suggested-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Aya Mahfouz <mahfouz.saif.elyazal@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 9a0791e..2f12bb9 100644
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -2336,7 +2336,7 @@
 	.get_icount = mxser_get_icount,
 };
 
-static struct tty_port_operations mxser_port_ops = {
+static const struct tty_port_operations mxser_port_ops = {
 	.carrier_raised = mxser_carrier_raised,
 	.dtr_rts = mxser_dtr_rts,
 	.activate = mxser_activate,