[WifiCoex] Fix VTS test for implemented hal

Fix coex VTS test by configuring chip for sta iface before invoking the
coex hal api.

Bug: 177929636
Test: atest VtsHalWifiV1_5TargetTest
Change-Id: I5ead53e603a2136e3c8b2d931c512e6d337f4ba7
1 file changed