Fix Suite B 192-bit AKM to use proper PMK length

Fix Suite B 192-bit AKM to use proper PMK length

In addition to the PTK length increasing, the length of the PMK was
increased (from 256 to 384 bits) for the 00-0f-ac:12 AKM. This part was
missing from the initial implementation and a fixed length (256-bit) PMK
was used for all AKMs.

Fix this by adding more complete support for variable length PMK and use
384 bits from MSK instead of 256 bits when using this AKM. This is not
backwards compatible with the earlier implementations.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>