amd64: Always include <config.h> in cipher assembly codes

* cipher/camellia-aesni-avx-amd64.S: Always include <config.h>.
* cipher/camellia-aesni-avx2-amd64.S: Likewise.
* cipher/serpent-avx2-amd64.S: Likewise.

When Intel CET is enabled, we need to include <cet.h> in assembly
codes to mark Intel CET support even if it is empty. We should
always include <config.h> in cipher amd64 assembly codes so that
they will be marked for Intel CET support when compiling for i686.

• Signed-off-by: H.J. Lu <hjl.tools@gmail.com>