There are some standard-based EAP-Methods available, but not PEAP.
But before using them you have to be aware of the consequences (from the AnyConnect Admin-Guide):
Note 
Changing the authentication method from the proprietary AnyConnect EAP to a standards-based method disables the ability of the ASA to configure session timeout, idle timeout, disconnected timeout, split tunneling, split DNS, MSIE proxy configuration, and other features.
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