As suggested by Wolfram Sang <w.sang@pengutronix.de>, use dev_dbg(),
and dev_{err,warn,info}() in pd6729.c, and add some "\n" suggested by
Komuro <komurojun-mbn@nifty.com>. In the ISR, use pr_devel() and
dev_vdbg() as they are only compiled if DEBUG (or, for dev_vdbg(),
VERBOSE_DEBUG) are set explicitly.

CC: Komuro <komurojun-mbn@nifty.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>