tty: make tty_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the tty_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/2023040250-landowner-unfitted-11f4@gregkh


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>