a2dp : pcm prepare fail for input during a2dp suspend and reconfig

Start input is failing due to race condition in a2dp suspend
and a2dp connection/disconnection. If a2dp suspend params are
and then a2dp disconnection comes, reseting the suspended
flag can cause a2dp_is_ready function return invalid value
during start input and hence pcm prepare fails.
Avoid setting a2dp suspend state to false if sco is still on.

Change-Id: I83950ddd0d4d3bbe6f30846cba48f6eb88c14690