The identity retrieved from simauth was required to include the
prefix for SIM/AKA/AKA', but in reality a real SIM would not
include that prefix in the IMSI. Now the correct prefix is
prepended onto the identity depending on the EAP method.
The EAP-method's .probe methods only checked the method name so do that
in eap.c instead and allocate method state in .load_settings. Rename
method's .remove method to .free to improve the naming.
EAP-AKA' uses SHA256 rather than SHA1 to generate the packet MAC's.
This updates the derive MAC API to take the EAP method type and
correctly use the right SHA variant to derive the MAC.
The AT_VERSION_LIST attribute length was not being properly
checked. The actual length check did not include possible padding
bytes, so align_len() was added to ensure it was padded properly.
The comment about the padding being included in the Master Key
generation was not correct (padding is NOT included), and was removed.
