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/engicam/common/spl.c b/board/engicam/common/spl.c
index 6359fb3..62b0678 100644
--- a/board/engicam/common/spl.c
+++ b/board/engicam/common/spl.c
@@ -7,6 +7,7 @@
 
 #include <common.h>
 #include <image.h>
+#include <init.h>
 #include <serial.h>
 #include <spl.h>