crypto: sha512 - Rename conflicting symbols

crypto: sha512 - Rename conflicting symbols

Rename existing functions and structs in architecture-optimized SHA-512
code that had names conflicting with the upcoming library interface
which will be added to <crypto/sha2.h>: sha384_init, sha512_init,
sha512_update, sha384, and sha512.

Note: all affected code will be superseded by later commits that migrate
the arch-optimized SHA-512 code into the library.  This commit simply
keeps the kernel building for the initial introduction of the library.

Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250630160320.2888-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>