gpio: fix build error in include/asm-generic/gpio.h

Should call the platform-specific __gpio_{get,set}_value
instead of generic gpio_{get,set}_value

Signed-off-by: Yang Bai <hamo.by@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>