drm/amd/display: amend HPD handler for Replay

[Why]
For Replay, if we receive HPD, it doesn’t need to reboot the display.
We don’t need to return anything exactly.

[How]
Return nothing just because we don’t need to reboot the display.

Signed-off-by: ChunTao Tso <chuntao.tso@amd.com>
Acked-by: Hersen Wu <hersenxs.wu@amd.com>
Reviewed-by: Jerry Zuo <jerry.zuo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>