crypto: aesni - make driver-gcm-aes-aesni helper a proper aead alg

crypto: aesni - make driver-gcm-aes-aesni helper a proper aead alg

Changed the __driver-gcm-aes-aesni to be a proper aead algorithm.
This required a valid setkey and setauthsize functions to be added and also
some changes to make sure that math context is not corrupted when the alg is
used directly.
Note that the __driver-gcm-aes-aesni should not be used directly by modules
that can use it in interrupt context as we don't have a good fallback mechanism
in this case.

Signed-off-by: Adrian Hoban <[email protected]>
Signed-off-by: Tadeusz Struk <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>