drm/amd/display: Add work around for AUX failure on wake.

[Why]
When waking from low-power states, a DP sink may remain unresponsive to
AUX transactions.

[How]
Try to toggle DPCD SET_POWER register repeatedly (up to a maximum
timeout value) until DP sink becomes responsive.

Reviewed-by: Mustapha Ghaddar <Mustapha.Ghaddar@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Jimmy Kizito <Jimmy.Kizito@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>