libwsbm: enable wsbm compiling for Baytrail platform

BZ: 96355

On baytrail platform, vp8 decoding is done by VXD.
While VXD decoding is using ttm as buffer manager,
there is no dependency on IMG gfx for wsbm compiling.
Signed-off-by: Fei Jiang <fei.jiang@intel.com>

Change-Id: Ic3671dc6369a64a4558e39bae333a78c3c60b5ad
Reviewed-on: http://android.intel.com:8080/98806
Reviewed-by: Ding, Haitao <haitao.ding@intel.com>
Tested-by: Ding, Haitao <haitao.ding@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>
1 file changed