ARM: ux500: included linux/gpio.h twice

arch/arm/mach-ux500/board-mop500-u8500uib.c included 'linux/gpio.h'
remove the duplicate.

Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
Acked-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>