drm/i915/dsi: Execute MIPI_SEQ_DEASSERT_RESET before calling device_ready()

Execute MIPI_SEQ_DEASSERT_RESET before putting the device in ready
state (LP-11), this is the sequence in which things should be done
according to the spec.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Bob Paauwe <bob.j.paauwe@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1488374106-4949-6-git-send-email-jani.nikula@intel.com