audioflinger: Fix glitches and volume ramp issue

 * Floating point support in the new mixer is not quite ready
   for prime time, and we have a number of failure cases.
 * Currently, we need features from the new mixer (multichannel,
   rebuffering) to support our codecs which output hires formats.
   These formats are all currently integer based (32-bit) and
   don't actually need float support.
 * Disable it for now to fix the issues until they are debugged.
 * Additionally, increase the size of the control block to deal
   with certain streams.

Change-Id: I8ee313193b24aa66e422f36d6c1c5359d025052c