When drivers are compiled in subdirectories the -DDEBUG flag need
to be passed in the individual Makefiles.
Reported-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Suggested-by: NYingjoe Chen <yingjoe.chen@mediatek.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>