Input: make input_class constant

Since commit 43a7206b09 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the input_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240305-class_cleanup-input-v1-1-0c3d950c25db@marliere.net
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/input.c

@@ -1918,7 +1918,7 @@ static char *input_devnode(const struct device *dev, umode_t *mode)
 	return kasprintf(GFP_KERNEL, "input/%s", dev_name(dev));
 }
 
-struct class input_class = {
+const struct class input_class = {
 	.name		= "input",
 	.devnode	= input_devnode,
 };