ftrace: Add comments to ftrace_hash_rec_disable/enable()

ftrace: Add comments to ftrace_hash_rec_disable/enable()

Add comments to describe what the functions ftrace_hash_rec_disable() and
ftrace_hash_rec_enable() do. Also change the passing of the "inc" variable
to __ftrace_hash_rec_update() to a boolean value as that is what it is
supposed to take.

Link: https://lore.kernel.org/linux-trace-kernel/20240605180408.857333430@goodmis.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>