staging: gasket: apex: Make structure apex_desc constant

Static structure apex_desc, of type gasket_driver_desc, is used only as
an argument to the functions gasket_register_device() and
gasket_unregister_device(). In the definitions of both these functions,
their parameter is declared as const. Hence make apex_desc itself
constant to protect it from modification.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190815054924.643-1-nishkadg.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/gasket/apex_driver.c

@@ -659,7 +659,7 @@ static void apex_pci_remove(struct pci_dev *pci_dev)
 	pci_disable_device(pci_dev);
 }
 
-static struct gasket_driver_desc apex_desc = {
+static const struct gasket_driver_desc apex_desc = {
 	.name = "apex",
 	.driver_version = APEX_DRIVER_VERSION,
 	.major = 120,