Fix doc reference to EVP_AEAD_max_overhead.

The documentation referred to the old name of |EVP_AEAD_overhead|.

Merged from Android's
https://android-review.googlesource.com/#/c/149947/

Change-Id: Ifd1b850355c8f7d9f3e990f514fa072d4cacef1c
diff --git a/include/openssl/aead.h b/include/openssl/aead.h
index b39939d..0416bbe 100644
--- a/include/openssl/aead.h
+++ b/include/openssl/aead.h
@@ -252,8 +252,8 @@
  *
  * At most |max_out_len| bytes are written to |out| and, in order to ensure
  * success, |max_out_len| should be |in_len| plus the result of
- * |EVP_AEAD_overhead|. On successful return, |*out_len| is set to the actual
- * number of bytes written.
+ * |EVP_AEAD_max_overhead|. On successful return, |*out_len| is set to the
+ * actual number of bytes written.
  *
  * The length of |nonce|, |nonce_len|, must be equal to the result of
  * |EVP_AEAD_nonce_length| for this AEAD.