Bluetooth: Remove unneeded crypto kconfig selections

Remove several kconfig selections that are no longer needed:

  - CRYPTO_SKCIPHER and CRYPTO_ECB have been unneeded since
    commit a4770e1117f1 ("Bluetooth: Switch SMP to
    crypto_cipher_encrypt_one()") in 2016.

  - CRYPTO_SHA256 has been unneeded since
    commit e7b02296fb40 ("Bluetooth: Remove BT_HS") in 2024.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>