drm/i915: Wait for VLV/CHV/BXT/GLK DSI panel power cycle delay on reboot

drm/i915: Wait for VLV/CHV/BXT/GLK DSI panel power cycle delay on reboot

As with eDP and LVDS we should also respect the power cycle
delay on DSI panels. We are not using the power sequencer
for these, and we have no optimizations around the sleep
duration, so we just msleep() the whole thing away.

Note that the ICL+ DSI code doesn't seem to have any power
off/power cycle delay handling whatsoever. The only thing it
handles is the power on delay. As that looks pretty busted
in general I won't bother dealing with it for the time being.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201001151640.14590-6-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>