tracing/hist: add in missing * in comment blocks

There are a couple of missing * in comment blocks. Fix these.
Cleans up two clang warnings:

kernel/trace/trace_events_hist.c:986: warning: bad line:
kernel/trace/trace_events_hist.c:3229: warning: bad line:

Link: https://lkml.kernel.org/r/20221020133019.1547587-1-colin.i.king@gmail.com



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