dm: Drop gpio.h header from fdtdec.c

Since GPIO support has now moved to the driver model uclass, we can drop
this include.

Signed-off-by: Simon Glass <sjg@chromium.org>

lib/fdtdec.c

@@ -11,8 +11,6 @@
 #include <fdtdec.h>
 #include <linux/ctype.h>
 
-#include <asm/gpio.h>
-
 DECLARE_GLOBAL_DATA_PTR;
 
 /*