drm/i915/glk: Add cold boot sequence for GLK DSI

As per BSEPC, if device ready bit is '0' in enable IO sequence
then its a cold boot/reset scenario eg: S3/S4 resume. If cold boot
scenario detected in enable IO, then prepare port immediately.
In normal boot scenario, prepare port after glk_dsi_device_ready().
Without cold boot sequence enabled, features like S3/S4 doesn't work.

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1497340095-5877-2-git-send-email-madhav.chauhan@intel.com