ftrace: Assign ftrace_list_end to ftrace_ops_list type cast to RCU

ftrace: Assign ftrace_list_end to ftrace_ops_list type cast to RCU

Use a type cast to convert ftrace_list_end to RCU when assigning
ftrace_ops_list. This will quiet the sparse warning:

 kernel/trace/ftrace.c:125:59: warning: incorrect type in initializer (different address spaces)
 kernel/trace/ftrace.c:125:59:    expected struct ftrace_ops [noderef] __rcu *[addressable] [toplevel] ftrace_ops_list
 kernel/trace/ftrace.c:125:59:    got struct ftrace_ops *

Link: https://lore.kernel.org/linux-trace-kernel/20240605202708.450784356@goodmis.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>