[build] Merge i386 and x86_64 versions of errfile.h

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/x86_64/include/bits/errfile.h

@@ -1,11 +0,0 @@
-#ifndef _BITS_ERRFILE_H
-#define _BITS_ERRFILE_H
-
-/**
- * @addtogroup errfile Error file identifiers
- * @{
- */
-
-/** @} */
-
-#endif /* _BITS_ERRFILE_H */