The name of the function emitting a log message may be of interest for a
developer but is distracting for normal users. See the example below:

    try_load_entry() Booting: Debian

Make the default format for log messages customizable. By default show
only the message text.
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: NSimon Glass <sjg@chromium.org>