wifi: ath12k: fix dp_link_peer dangling references on AP vdev rollback

In the Linux kernel, the following vulnerability has been resolved:

wifi: ath12k: fix dp_link_peer dangling references on AP vdev rollback

ath12k_mac_vdev_create() for an AP vdev creates the bss self-peer via
ath12k_peer_create(), which finishes by calling
ath12k_dp_link_peer_assign() to publish the dp_link_peer in the
dp_hw->dp_peers[peerid_index] RCU table, in the dp_peer's
link_peers[] array, and in the per-addr rhashtable.

If a step after ath12k_peer_create() fails the function jumps to
err_peer_del, which open-codes a WMI peer_delete and waits for the
unmap / delete_resp events. The wait_for_peer_delete_done() path
relies on ath12k_dp_link_peer_unmap_event() freeing the dp_link_peer
when the unmap arrives, but err_peer_del never calls
ath12k_dp_link_peer_unassign() first. The published references in
the dp_hw RCU table, dp_peer->link_peers[] and the rhashtable are
left pointing at the dp_link_peer that unmap_event then frees,
producing dangling pointers and use-after-free on subsequent
lookups.

Replace the open-coded sequence with a call to ath12k_peer_delete(),
which already does ath12k_dp_link_peer_unassign() before sending the
WMI command. This drops the published references before the
dp_link_peer is freed, in the same order as the normal teardown path
in ath12k_mac_remove_link_interface().

Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.1.c7-00108-QCAHMTSWPL_V1.0_V2.0_SILICONZ_UPSTREAM-3