crypto: speck - remove Speck

These are unused, undesired, and have never actually been used by
anybody. The original authors of this code have changed their mind about
its inclusion. While originally proposed for disk encryption on low-end
devices, the idea was discarded [1] in favor of something else before
that could really get going. Therefore, this patch removes Speck.

[1] https://marc.info/?l=linux-crypto-vger&m=153359499015659

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Eric Biggers <ebiggers@google.com>
Cc: stable@vger.kernel.org
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/filesystems/fscrypt.rst

@@ -191,21 +191,11 @@ Currently, the following pairs of encryption modes are supported:
 
 - AES-256-XTS for contents and AES-256-CTS-CBC for filenames
 - AES-128-CBC for contents and AES-128-CTS-CBC for filenames
-- Speck128/256-XTS for contents and Speck128/256-CTS-CBC for filenames
 
 It is strongly recommended to use AES-256-XTS for contents encryption.
 AES-128-CBC was added only for low-powered embedded devices with
 crypto accelerators such as CAAM or CESA that do not support XTS.
 
-Similarly, Speck128/256 support was only added for older or low-end
-CPUs which cannot do AES fast enough -- especially ARM CPUs which have
-NEON instructions but not the Cryptography Extensions -- and for which
-it would not otherwise be feasible to use encryption at all.  It is
-not recommended to use Speck on CPUs that have AES instructions.
-Speck support is only available if it has been enabled in the crypto
-API via CONFIG_CRYPTO_SPECK.  Also, on ARM platforms, to get
-acceptable performance CONFIG_CRYPTO_SPECK_NEON must be enabled.
-
 New encryption modes can be added relatively easily, without changes
 to individual filesystems.  However, authenticated encryption (AE)
 modes are not currently supported because of the difficulty of dealing