dsp: Fix open params for read_compr in IEC61937 mode

The read compressed in IEC61937 mode doesn't unpack data to frames, but
data flow still requires frames_per_buf to be set to nonzero value.

Change-Id: Idb09219c57d7790cb90df62c97baf3ef0e9d8a2f
Signed-off-by: Ralf Herz <rherz@codeaurora.org>