Bluetooth: controller: Fix central enc termination

Terminate connection with a MIC failure if an unexpected control PDU
is received during the Encryption Start procedure.

Add a greedy option to pdu_is_expected() to make sure the procedure
processes all unexpected control PDU in all cases.

Add unit test inspired by Bluetooth Qualification test
LL/SEC/CEN/BV-14-C,
Central Receiving unexpected PDU during encryption start

Signed-off-by: Thomas Ebert Hansen <thoh@oticon.com>