dm: sandbox: i2c: Drop fdtdec.h header

This is not needed in this driver. Drop it.
Signed-off-by: NSimon Glass <sjg@chromium.org>

drivers/i2c/sandbox_i2c.c

@@ -9,7 +9,6 @@
 #include <common.h>
 #include <dm.h>
 #include <errno.h>
-#include <fdtdec.h>
 #include <i2c.h>
 #include <asm/test.h>
 #include <dm/lists.h>