wireguard: kconfig: simplify crypto kconfig selections

wireguard: kconfig: simplify crypto kconfig selections

Simplify the kconfig entry for WIREGUARD:

- Drop the selections of the arch-optimized ChaCha20, Poly1305, BLAKE2s,
  and Curve25519 code.  These options no longer exist, as lib/crypto/
  now enables the arch-optimized code automatically.

- Drop the selection of CRYPTO.  This was needed only to make the
  arch-optimized options visible.  lib/crypto/ now handles these options
  internally, without any dependency on CRYPTO.

- Drop the dependency on !KMSAN.  This was needed only to avoid
  selecting arch-optimized code that isn't compatible with KMSAN.
  lib/crypto/ now handles the !KMSAN dependencies internally.

- Add a selection of CRYPTO_LIB_UTILS, since WireGuard directly calls
  crypto_memneq().  This gets selected indirectly by
  CRYPTO_LIB_CURVE25519 and CRYPTO_LIB_CHACHA20POLY1305 anyway, but it's
  best to make this dependency explicit.

Link: https://lore.kernel.org/r/20250906213523.84915-13-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>