pinctrl: nand: meson-gxl: fix missing data pins

The data pin 0-7 of the NAND controller are actually missing from
the nand pinctrl group, so we fix it here.

Fixes: 0f15f500 ("pinctrl: meson: Add GXL pinctrl definitions")
Reported-by: Liang Yang <liang.yang@amlogic.com>
Signed-off-by: Yixun Lan <yixun.lan@amlogic.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>