wifi: ath12k: vdev statemachine changes for single wiphy

With single wiphy, multiple radios are combined into a single wiphy.
Since any channel can be assigned to a vif being brought up,
the vdev cannot be created during add_interface(). Hence defer the
vdev creation till channel assignment.

If only one radio is part of the wiphy, then the existing logic
is maintained, i.e vdevs are created during add interface and
started during channel assignment. This ensures no functional changes
to single pdev devices which has only one radio in the SoC.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.0.1-00029-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: Sriram R <quic_srirrama@quicinc.com>
Signed-off-by: Rameshkumar Sundaram <quic_ramess@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240405194519.1337906-5-quic_ramess@quicinc.com