[PORT FROM R2] Audio: enable CONFIG_SND_ALOOP to get Alsa loopback virtual soundcard

[PORT FROM R2] Audio: enable CONFIG_SND_ALOOP to get Alsa loopback virtual soundcard

BZ: 6685

To enable the Alsa loopback virtual device, the CONFIG_SND_ALOOP must be
set to yes to get snd-aloop built and linked to the kernel.
This virtual sound card consists of 2 devices:

hw:Loopback,0
hw:Loopback,1
If an application outputs its audio to one of the subdevices e.g. say
hw:Loopback,0,0 the audio will be available as input in the corresponding
subdevice hw:Loopback,1,0 because the whole point for this card is to
send the signal back to itself.

The loopback soundcard is needed to enable WiDi capability, as detailled
in use case description of P_UC_20322.

Note: Cherry pick of Change-Id: I61acb233c5568b80b0d6e9f1f12ad6c673953eb3 to ICS branch
did not work in enabling the loopback virtual soundcard. CONFIG_SND_ALOOP needs to be
enabled after the CONFIG_SND_DRIVERS.

Change-Id: Ia350cd40ce3dd558a6eb24c3ac5ed971649677bd
Orig-Change-id: I61acb233c5568b80b0d6e9f1f12ad6c673953eb3
Signed-off-by: Rajneesh Chowdhury <rajneeshx.chowdhury@intel.com>
Reviewed-on: http://android.intel.com:8080/31589
Reviewed-by: Soulard, MathieuX <mathieux.soulard@intel.com>
Reviewed-by: Veeramani, Karthik <karthik.veeramani@intel.com>
Reviewed-by: Poornachandran, Rajesh <rajesh.poornachandran@intel.com>
Reviewed-by: Gross, Mark <mark.gross@intel.com>
Reviewed-by: Marotte, Fabien <fabien.marotte@intel.com>
Reviewed-by: Bachot, Jean-michelX <jean-michelx.bachot@intel.com>
Tested-by: Zurmely, PierreX <pierrex.zurmely@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>