pinctrl: pinctrl-imx: only print debug message when DEBUG is defined

Fix regression for commit 3a86a5f8 (pinctrl: pinctrl-imx: free allocated
pinctrl_map structure only once and use kernel facilities for IMX_PMX_DUMP)
introduced in 3.5-rc3.
With above commit, the debug code will alway be excuted.
Change to excute it only when DEBUG is defined.

Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>