DPCD 600h - SET_POWER & SET_DP_PWR_VOLTAGE defines power state

101 = Set Main-Link for local Sink device and all downstream Sink
devices to D3 (power-down mode), keep AUX block fully powered, ready to
reply within a Response Timeout period of 300us.

This state is useful in a MST dock + MST monitor configuration that
doesn't wake up from D3 state.

v2: Use spaces instead of tabs (Jani)

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1502475008-2035-1-git-send-email-dhinakaran.pandiyan@intel.com