image-fit: Fix compiling error caused by autoconf.h

Commit ec6617c3 includes autoconf.h in image-fit.c, causing conflict
for board odroid-xu3 which overwrites CONFIG_SYS_BOARD in header
file. Move the include higher and use linux/kconfig.h instead of
generated/autoconf.h.

Signed-off-by: York Sun <york.sun@nxp.com>
CC: Alison Wang <alison.wang@nxp.com>
diff --git a/common/image-fit.c b/common/image-fit.c
index ea56d5b..9468e51 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -14,6 +14,7 @@
 #include <time.h>
 #else
 #include <linux/compiler.h>
+#include <linux/kconfig.h>
 #include <common.h>
 #include <errno.h>
 #include <mapmem.h>
@@ -27,7 +28,6 @@
 #include <u-boot/md5.h>
 #include <u-boot/sha1.h>
 #include <u-boot/sha256.h>
-#include <generated/autoconf.h>
 
 /*****************************************************************************/
 /* New uImage format routines */