qcacld-3.0: Remove wma_sta_send_vdev_down_bss() prototype
Change Iee7274fbc8ae985d034a29f920faa38aab68ccc7 ("qcacld-3.0: Add
VDEV state machine for STA disconnection") removed the implementation
of function wma_sta_send_vdev_down_bss(). However it left behind the
prototype, so remove it now.
Change-Id: Ia43371f6c86632955f67370d3ffc9b2753f797f7
CRs-Fixed: 2379064