ftrace: Remove unused extern declarations

ftrace: Remove unused extern declarations

commit 6a9c981b1e96 ("ftrace: Remove unused function ftrace_arch_read_dyn_info()")
left ftrace_arch_read_dyn_info() extern declaration.
And commit 1d74f2a0f64b ("ftrace: remove ftrace_ip_converted()")
leave ftrace_ip_converted() declaration.

Link: https://lore.kernel.org/linux-trace-kernel/20230725134808.9716-1-yuehaibing@huawei.com
Cc: <mhiramat@kernel.org>
Cc: <mark.rutland@arm.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>