Fix typos, inconsistencies in using quotes, incorrect section number,
etc. in the trace histogram documentation.

Link: http://lkml.kernel.org/r/20180614224859.55864-1-joel@joelfernandes.orgReviewed-by: NMasami Hiramatsu <mhiramat@kernel.org>
Acked-by: NTom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: NJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>