staging: mt7621-gpio: avoid locking in mediatek_gpio_get_direction

mediatek_gpio_get_direction function is holding across a simple read
which it seems to be not neccessary at all. Just remove this locking
cleaning code of this function a bit.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>