commands: dmesg: fi format security warning ...

commands/dmesg.c: In function ‘do_dmesg’:
commands/dmesg.c:71:3: warning: format not a string literal and no format arguments [-Wformat-security]

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Introduce message logging support ...

This adds a buffer for log messages and a 'dmesg' command to
print the messages. The log buffer is implemented as log objects
rather than a string buffer. This makes it easy to implement
limiting the messages, cleaning the buffer and timestamping
the messages.

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