As written, the title and description of the Kconfig option seem to
specify the logging sub-system will not flush until the buffer is full.
Someone reading this would expect that shorter log message will not be
flushed until the specified number of bytes accumulate.
This is not the case. Each log message is flushed when finished. The
size is only the maximum bytes of a single formatted message's contents
that will be accumated before the backend flushes.
What's more, it only applies in deferred mode. In immediate mode there
is no buffering, not just of multiple log messages but also of the
message contents as they are formatted.
Signed-off-by: Trent Piepho <tpiepho@gmail.com>