types: Introduce [us]128

Introduce [us]128 (when available). Unlike [us]64, ensure they are
always naturally aligned.

This also enables 128bit wide atomics (which require natural
alignment) such as cmpxchg128().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20230531132323.385005581@infradead.org

crypto: curve25519 - generic C library implementations

This contains two formally verified C implementations of the Curve25519
scalar multiplication function, one for 32-bit systems, and one for
64-bit systems whose compiler supports efficient 128-bit integer types.
Not only are these implementations formally verified, but they are also
the fastest available C implementations. They have been modified to be
friendly to kernel space and to be generally less horrendous looking,
but still an effort has been made to retain their formally verified
characteristic, and so the C might look slightly unidiomatic.

The 64-bit version comes from HACL*: https://github.com/project-everest/hacl-star
The 32-bit version comes from Fiat: https://github.com/mit-plv/fiat-crypto

Information: https://cr.yp.to/ecdh.html

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
[ardb: - move from lib/zinc to lib/crypto
- replace .c #includes with Kconfig based object selection
- drop simd handling and simplify support for per-arch versions ]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>