pinctrl: pinctrl-imx: fix incorrect debug message of maps

After create config map, the new_map pointer becomes point to
PIN_MAP_TYPE_CONFIGS_PIN map rather than PIN_MAP_TYPE_MUX_GROUP map any more.
Thus using new_map pointer to display the MUX_GROUP info is not correct.
Using map pointer instead to show the correct MUX_GROUP map info.
Original the debug message is:
imx6q-pinctrl 20e0000.iomuxc: maps: function Yp group MX6Q_PAD_SD3_CMD num 12
After fix it is:
imx6q-pinctrl 20e0000.iomuxc: maps: function usdhc3 group usdhc3grp-1 num 11

Reported-by: Richard Zhao <richard.zhao@freescale.com>
Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>