crypto: arm64/gcm - add RFC4106 support

Add support for RFC4106 ESP encapsulation to the accelerated GCM
implementation. This results in a ~10% speedup for IPsec frames of
typical size (~1420 bytes) on Cortex-A53.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>