arm: Use sections header to obtain link symbols

Include this header to get access to link symbols, which are otherwise
removed.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/cm4008/flash.c b/board/cm4008/flash.c
index 5522bf0..0faf197 100644
--- a/board/cm4008/flash.c
+++ b/board/cm4008/flash.c
@@ -29,6 +29,7 @@
 
 #include <common.h>
 #include <linux/byteorder/swab.h>
+#include <asm/sections.h>
 
 
 flash_info_t flash_info[CONFIG_SYS_MAX_FLASH_BANKS];	/* info for FLASH chips */