crypto: aes - helper function to validate key length for AES algorithms

Add inline helper function to check key length for AES algorithms.
The key can be 128, 192 or 256 bits size.
This function is used in the generic aes implementation.

Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>