[tegra ALSA] Support built-in speaker

[tegra ALSA] Support built-in speaker

Added support for built-in speaker. Although audio subsystem on
different boards have various topology, Tegra boards usually have
amplifier connected to codec. The patch added a control interface to
expose speaker control widget to user space. Amplifier could be driven
automatically if internal speaker turned on.

fixes bug 766757

Change-Id: Ic6b8d0c58830a71ff8d6c09d1268cbd97982d08b
Reviewed-on: http://git-master/r/21985
Reviewed-by: Chao Jiang <chaoj@nvidia.com>
Tested-by: Chao Jiang <chaoj@nvidia.com>
Reviewed-by: Scott Peterson <speterson@nvidia.com>