Remove references to AEAD in non-AEAD interface codepath

Since all AEAD ciphers now go through EVP_AEAD interface, the code which
uses EVP_Cipher interface no longer needs any of AEAD handling logic.

This also removes EVP_CTRL_AEAD_TLS1_AAD from GCM interface, which was
duplicating non-TLS-specific GCM logic and is not used anymore.

Change-Id: I5ddae880e7bc921337f9149a0acfdd00c9a478c3