pinctrl: meson: Fix eth_tx_en bit index

Fix pinctrl eth_tx_en bit index according to Hardkernel ODROID-C1 datasheet.

Signed-off-by: Alexander Müller <serveralex@gmail.com>
Acked-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>