Loglevel 7 (debug) is often useful to get barebox running on new
hardware; however, the heavy output of "OF:" messages makes most
boards take several minutes to boot to a prompt, printing things which
are probably interesting when debugging OF code itself, but not very
helpful otherwise. Degrade most of the message to loglevel 8 (vdebug).

Signed-off-by: Roland Hieber <rhi@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>