common: Drop init.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/technexion/pico-imx6ul/pico-imx6ul.c b/board/technexion/pico-imx6ul/pico-imx6ul.c
index 4294f3e..e4ca83a 100644
--- a/board/technexion/pico-imx6ul/pico-imx6ul.c
+++ b/board/technexion/pico-imx6ul/pico-imx6ul.c
@@ -5,6 +5,7 @@
  * Author: Richard Hu <richard.hu@technexion.com>
  */
 
+#include <init.h>
 #include <net.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/iomux.h>