ring-buffer: Make the const read-only 'type' static

Don't populate the read-only 'type' on the stack at run time,
instead make it static.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250714160858.1234719-1-colin.i.king@gmail.com


Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>