x86: Support loading kernel setup from a FIT

Add a new setup@ section to the FIT which can be used to provide a setup
binary for booting Linux on x86. This makes it possible to boot x86 from
a FIT.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index 843ec6e..6723360 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -12,6 +12,7 @@
 #include <bootm.h>
 #include <command.h>
 #include <environment.h>
+#include <errno.h>
 #include <image.h>
 #include <lmb.h>
 #include <malloc.h>