arch/arm/mach-pxa/: included linux/gpio.h twice

arch/arm/mach-pxa/pxa25x.c and arch/arm/mach-pxa/saarb.c
included 'linux/gpio.h' twice, remove the duplicates.

Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>