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/zyxel/nsa310s/nsa310s.c b/board/zyxel/nsa310s/nsa310s.c
index 82a3fee..3f71e3d 100644
--- a/board/zyxel/nsa310s/nsa310s.c
+++ b/board/zyxel/nsa310s/nsa310s.c
@@ -6,6 +6,7 @@
  */
 
 #include <common.h>
+#include <init.h>
 #include <miiphy.h>
 #include <net.h>
 #include <asm/arch/cpu.h>