alsa_sound: Fix for multiple streams being opened during boot-up

- Multiple streams (Fast/LPA/Tunnel/VoIP) were getting opened
during boot up.
- Becuase of this, Fast output was getting converted to Direct
Output and Direct output was resued by LPA/Tunnel/VoIP which
was leading to crash scenario, also voting against TCXO shutdown.
- QCOM_OUTPUT_FLAGS_ENABLED was defined in AudioPolicy, which avoids
opening of multiple streams. This fixed crash & TCXO shutdown.

 CRs-Fixed: 502834, 513200

Change-Id: If1393b1e12561acc0d0ac352de42194175947c5a