include/fix_u32.h: try harder to not cause redefinition errors

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

include/fix_u32.h

@@ -8,6 +8,17 @@
 #ifndef FIX_U32_H
 #define FIX_U32_H 1
 
+/* Try hard to pull in u32 types and such.
+ * Otherwise, #include "fix_u32.h" + #include <linux/foo.h>
+ * may end up typedef'ing bb_hack_u32 inside foo.h,
+ * and repeated typedefs aren't allowed in C/C++.
+ */
+#include <asm/types.h>
+#include <linux/types.h>
+
+/* In case above includes still failed to provide the types,
+ * provide them ourself
+ */
 #undef __u64
 #undef u64
 #undef u32