asoc: adapt to new compressed format header

snd_enc_generic structure is used to pass the decoder type
and configuration. Reserved[0] contains the decoder type
and reserve[1] onwards the decoder configuration. Adapt
decoder parsing logic accordingly.

Change-Id: Icc0bf27e026e0144e8356abddf7646a6d34e645c
Signed-off-by: Xiaojun Sang <xsang@codeaurora.org>