drm/i915/icl: Set TBT IO in Aux transaction

For a TBT sequence, we need to set the IO type to TBT
in  DDI_AUX_CTL.

v2: Avoid duplications.(Paulo)

Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1532648115-29795-2-git-send-email-anusha.srivatsa@intel.com