crypto: chacha - register only "-lib" drivers

For the "chacha20", "xchacha20", and "xchacha12" skcipher algorithms,
instead of registering "*-generic" drivers as well as conditionally
registering "*-$(ARCH)" drivers, instead just register "*-lib" drivers.
These just use the regular library functions, so they just do the right
thing and are fully accelerated when supported by the CPU.

This eliminates the need for the ChaCha library to support
chacha_crypt_generic() and hchacha_block_generic() as part of its
external interface.  A later commit will make chacha_crypt_generic() a
static function.

Since this commit removes several "*-generic" driver names which
crypto/testmgr.c expects to exist, update testmgr.c accordingly.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250827151131.27733-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

crypto/Kconfig

@@ -648,7 +648,6 @@ config CRYPTO_ARC4
 config CRYPTO_CHACHA20
 	tristate "ChaCha"
 	select CRYPTO_LIB_CHACHA
-	select CRYPTO_LIB_CHACHA_GENERIC
 	select CRYPTO_SKCIPHER
 	help
 	  The ChaCha20, XChaCha20, and XChaCha12 stream cipher algorithms