fit: fixed bug in locate_dtb_in_fit()

If the dtb is the first data of the FIT, the its offset is 0x0. Change the
test to '<' instead of '<='

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

common/boot_fit.c

@@ -73,7 +73,7 @@ void *locate_dtb_in_fit(const void *fit)
 
 	ret = fdt_offset(fit);
 
-	if (ret <= 0)
+	if (ret < 0)
 		return NULL;
 	else
 		return (void *)fit+size+ret;