p2p: refine random 2.4GHz GO channel selection

2.4GHz channels might be restricted due to cellular coex and
there is no channel availability check after selecting a channel
randomly. When the selected channel is not available, iterate through
other possible 2.4GHz channels until an available channel is found.

Bug: 204409430
Test: start GO on 2.4Ghz band
Change-Id: Ie9a1ed9e3a76f1aa044345aed475ef5061e0632f
1 file changed