tracing: Use tracing error_log with hist triggers

Replace hist_err() and hist_err_event() with tracing_log_err() from
the new tracing error_log mechanism.

Also add a couple related helper functions and remove most of the old
hist_err()-related code.

With this change, users no longer read the hist files for hist trigger
error information, but instead look at tracing/error_log for the same
information.

Link: http://lkml.kernel.org/r/c98f77a97c9715d18b623eeb5741057b330d5ac0.1554072478.git.tom.zanussi@linux.intel.com

Acked-by: Masami Hiramatsu <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

Author: tzanussi