Convert the glue code for the PowerPC SPE implementations of AES-ECB,
AES-CBC, AES-CTR, and AES-XTS from the deprecated "blkcipher" API to the
"skcipher" API.  This is needed in order for the blkcipher API to be
removed.

Tested with:

	export ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu-
	make mpc85xx_defconfig
	cat >> .config << EOF
	# CONFIG_MODULES is not set
	# CONFIG_CRYPTO_MANAGER_DISABLE_TESTS is not set
	CONFIG_DEBUG_KERNEL=y
	CONFIG_CRYPTO_MANAGER_EXTRA_TESTS=y
	CONFIG_CRYPTO_AES=y
	CONFIG_CRYPTO_CBC=y
	CONFIG_CRYPTO_CTR=y
	CONFIG_CRYPTO_ECB=y
	CONFIG_CRYPTO_XTS=y
	CONFIG_CRYPTO_AES_PPC_SPE=y
	EOF
	make olddefconfig
	make -j32
	qemu-system-ppc -M mpc8544ds -cpu e500 -nographic \
		-kernel arch/powerpc/boot/zImage \
		-append cryptomgr.fuzz_iterations=1000

Note that xts-ppc-spe still fails the comparison tests due to the lack
of ciphertext stealing support.  This is not addressed by this patch.

This patch also cleans up the code by making ->encrypt() and ->decrypt()
call a common function for each of ECB, CBC, and XTS, and by using a
clearer way to compute the length to process at each step.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>