DHKey check failed when using rpa_pub on both sides

[michal-narajowski]

Pairing fails after initiator confirms passkey number.
Fails with reason "DHKey check failed (0x0b)". Tested using btshell with
the following configuration on both sides:

BLE_SM_BONDING: 1
BLE_SM_OUR_KEY_DIST: 7
BLE_SM_THEIR_KEY_DIST: 7
BLE_SM_IO_CAP: 4
BLE_SM_MITM: 1
BLE_SM_SC: 1
BLE_MONITOR_RTT: 1
BLE_EXT_ADV: 1
BLE_L2CAP_COC_MAX_NUM: 2
BLE_RPA_TIMEOUT: 600
BLE_EXT_ADV_MAX_SIZE: 1650
BLE_LL_CFG_FEAT_LE_2M_PHY: 1
BLE_LL_CFG_FEAT_LE_CODED_PHY: 1

Steps to reproduce

Device A:

advertise-configure connectable=1 legacy=1 scannable=1 own_addr_type=rpa_pub
advertise-set-adv-data flags=6 name=codecoup
advertise-start

Device B:

connect peer_addr=<rpa addr> peer_addr_type=random own_addr_type=rpa_pub
security-pair conn=1

Now there are two options:

Option 1:
Device B:

auth-passkey conn=1 action=4 yesno=y
Pairing fails here!

Option 2:
Device A:

auth-passkey conn=1 action=4 yesno=y

Device B:

auth-passkey conn=1 action=4 yesno=y
Pairing fails here!

[michal-narajowski]

Fixed by #332