ath11k: start vdev if a bss peer is already created

For QCA6390, bss peer must be created before vdev is to start. This
change is to start vdev if a bss peer is created. Otherwise, ath11k
delays to start vdev.

This fixes an issue in a case where HT/VHT/HE settings change between
authentication and association, e.g., due to the user space request
to disable HT.

Tested-on: QCA6390 hw2.0 PCI WLAN.HST.1.0.1-01740-QCAHSTSWPLZ_V2_TO_X86-1

Signed-off-by: Carl Huang <cjhuang@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201211051358.9191-1-cjhuang@codeaurora.org