Bluetooth: legacy advertising doesn't resume if CONFIG_BT_EXT_ADV=y

[jori-nordic]

Describe the bug In this configuration: HCI over RPMSG, CONFIG_BT_EXT_ADV=y, CONFIG_BT_MAX_CONN>1:

• a legacy advertiser is started using bt_le_adv_start, without setting BT_LE_ADV_OPT_ONE_TIME.
• a device connects
• bt_le_adv_resume fails to resume the advertiser

See the original discussion in https://github.com/zephyrproject-rtos/zephyr/pull/51309 .

edit: wasn't really related to nRF53, also reproduced with just a single device with CONFIG_BT_EXT_ADV=y.

To Reproduce Steps to reproduce the behavior:

• flash samples/bluetooth/peripheral with the following config: CONFIG_BT_MAX_CONN=2, CONFIG_BT_EXT_ADV=y to the nRF5340 app core.
• flash samples/bluetooth/hci_rpmsg with the following config: CONFIG_BT_MAX_CONN=2, CONFIG_BT_EXT_ADV=y to the nRF5340 net core.

Expected behavior Advertising resumes after a connection is established.

[kruithofa]

@jhedberg can you have a look?

[jori-nordic]

@tgagneret-embedded could you double-check if the merged patch fixes your original issue?