ASoC: msm: set the master gain to 0 on DSP while configuring

- Mute media volume and play any music clip then reboot
  the phone. Play music again noise comes. This noise
  is introduced in DSP/LPASS.

- DSP suggestion is to mute master volume gain while
  configuring ASM session to avoid such noise at
  begining of asm playback.

Change-Id: I2aa2846d6e3e9a85c459534e9108e6fe7aebb962
Signed-off-by: Ramjee Singh <ramjee@codeaurora.org>
ASoC: msm: Fix for wma playback after SSR

After SSR apr session doesn't get destroyed as
the callback from apr driver doesn't come.Fix
this by not doing NULL allocation in q6asm callback.

Change-Id: Idfec89dfd06075fec4199869354bdcb9e01a3dc9
Signed-off-by: Anish Kumar <kanish@codeaurora.org>