composer: Initialize the cached active config index

Initialize the cached active config index by GetActiveConfig api.
This is required because DAL can initialize the active config to the
preferred config, flagged with DRM_MODE_TYPE_PREFERRED by DRM driver.

CRs-Fixed: 2683410
Change-Id: I48110dfcee2c281825a20f87d10274450779c7bf
1 file changed