tools lib traceevent: Rename tep_is_file_bigendian() to tep_file_bigendian()

In order to make libtraceevent into a proper library, its API
should be straightforward.

After a discussion with Steven Rostedt, we decided to rename a few APIs,
to have more intuitive names.

This patch renames tep_is_file_bigendian() to tep_file_bigendian().

Signed-off-by: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20181201040852.767549746@goodmis.org


Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>