drm/i915/icl: Fix port disable sequence for mipi-dsi

Re-enable clock gating of DDI clocks.

v2: Fix the default ddi clk state for mipi-dsi (Imre)

Fixes: 1026bea0

 ("drm/i915/icl: Ungate DSI clocks")
Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1553513202-13863-2-git-send-email-vandita.kulkarni@intel.com