lib/crypto: riscv/aes: Migrate optimized code into library

Move the aes_encrypt_zvkned() and aes_decrypt_zvkned() assembly
functions into lib/crypto/, wire them up to the AES library API, and
remove the "aes-riscv64-zvkned" crypto_cipher algorithm.

To make this possible, change the prototypes of these functions to
take (rndkeys, key_len) instead of a pointer to crypto_aes_ctx, and
change the RISC-V AES-XTS code to implement tweak encryption using the
AES library instead of directly calling aes_encrypt_zvkned().

The result is that both the AES library and crypto_cipher APIs use
RISC-V's AES instructions, whereas previously only crypto_cipher did
(and it wasn't enabled by default, which this commit fixes as well).

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260112192035.10427-15-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>

lib/crypto/Makefile

@@ -50,6 +50,7 @@ OBJECT_FILES_NON_STANDARD_powerpc/aesp8-ppc.o := y
 endif # !CONFIG_SPE
 endif # CONFIG_PPC
 
+libaes-$(CONFIG_RISCV) += riscv/aes-riscv64-zvkned.o
 endif # CONFIG_CRYPTO_LIB_AES_ARCH
 
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