MLK-17491-10 pinctrl: imx: remove gpio_set_direction_scu

MLK-17491-10 pinctrl: imx: remove gpio_set_direction_scu

There's no meaning to add gpio_set_direction-scu function as 1) current
pinctrl binding does not claim any GPIO direction setting capbility and
2) no GPIO driver actually uses it.

And current implementation also simply return a -EINVAL error which is
meainingless too.

Cc: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Fixes: 5d7a13220ade ("MLK-15128-3 pinctrl: freescale: support scu and memmap pinctrl together")
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>