gpio: viperboard: Remove duplicate code to set gpio->gpiob_val

Set it once is enough, and it's done in vprbrd_gpiob_set() which is called by
vprbrd_gpiob_direction_output().

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Tested-by: Lars Poeschel <poeschel@lemonage.de>
Acked-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>