smb: client: Use AES-CMAC library for SMB3 signature calculation

smb: client: Use AES-CMAC library for SMB3 signature calculation

Convert smb3_calc_signature() to use the AES-CMAC library instead of a
"cmac(aes)" crypto_shash.

The result is simpler and faster code.  With the library there's no need
to allocate memory, no need to handle errors except for key preparation,
and the AES-CMAC code is accessed directly without inefficient indirect
calls and other unnecessary API overhead.

For now a "cmac(aes)" crypto_shash is still being allocated in
'struct cifs_secmech'.  Later commits will remove that, simplifying the
code even further.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>