AES uses the same 128-bit block size with 128, 192, 256 bit keys, so use
the fixed block size definition instead of trying to dynamically set the
block size based on key length. This fixes use of 192-bit and 256-bit
AES keys with crypto_cipher_*() API when using the internal AES
implementation.
Signed-hostap: Jouni Malinen <j@w1.fi>