drm/amd/display: Avoid HPD IRQ in GPU reset state

[Why]
If GPU is in reset state, force enabling link will cause
unexpected behaviour.

[How]
Avoid handling HPD IRQ when GPU is in reset state.

Signed-off-by: Zhan Liu <zhan.liu@amd.com>
Reviewed-by: Nikola Cornij <nikola.cornij@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>