All of the functions using debug() in that file have enough info to
use dev_dbg instead. Convert all of the uses of debug() to dev_dbg()
in order to get more informative debug output.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>