Hexagon: misc compile warning/error cleanup due to missing headers

Fixed warnings/errors for EXPORT_SYMBOL, linux_binprm, elf related
defines

Signed-off-by: Richard Kuo <rkuo@codeaurora.org>
diff --git a/arch/hexagon/kernel/vdso.c b/arch/hexagon/kernel/vdso.c
index f212a45..5d39f42 100644
--- a/arch/hexagon/kernel/vdso.c
+++ b/arch/hexagon/kernel/vdso.c
@@ -21,6 +21,7 @@
 #include <linux/err.h>
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
+#include <linux/binfmts.h>
 
 #include <asm/vdso.h>