Fix compile warnings with CONFIG_PM=n

arch/powerpc/platforms/powermac/feature.c:489: warning: 'save_gpio_levels' defined but not used
arch/powerpc/platforms/powermac/feature.c:490: warning: 'save_gpio_extint' defined but not used
arch/powerpc/platforms/powermac/feature.c:491: warning: 'save_gpio_normal' defined but not used
arch/powerpc/platforms/powermac/feature.c:492: warning: 'save_unin_clock_ctl' defined but not used
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>