staging: gdm724x: constify tty_port_operations structs

Constifies tty_port_operations structure in
the tty code of the gdm724x driver since it
is not modified after its initialization.

Detected and found using Coccinelle.
Suggested-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NAya Mahfouz <mahfouz.saif.elyazal@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gdm724x/gdm_tty.c

@@ -64,7 +64,7 @@ static void gdm_port_destruct(struct tty_port *port)
 	kfree(gdm);
 }
 
-static struct tty_port_operations gdm_port_ops = {
+static const struct tty_port_operations gdm_port_ops = {
 	.destruct = gdm_port_destruct,
 };