fdt: Include arch specific gpio.h instead of asm-generic/gpio.h

Include arch specific gpio.h instead of asm-generic/gpio.h
because several architectures (Microblaze, Blackfin, Nios2, OpenRISC)
define gpio functions in header file.
asm-generic/gpio.h can be included in arch specific gpio.h
(For example: ARM)

Signed-off-by: Michal Simek <monstr@monstr.eu>
CC: Simon Glass <sjg@chromium.org>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Simon Glass <sjg@chromium.org>

lib/fdtdec.c

@@ -24,8 +24,7 @@
 #include <libfdt.h>
 #include <fdtdec.h>
 
-/* we need the generic GPIO interface here */
-#include <asm-generic/gpio.h>
+#include <asm/gpio.h>
 
 DECLARE_GLOBAL_DATA_PTR;