drm/amd/display: Make GPIO HPD path conditional

drm/amd/display: Make GPIO HPD path conditional

[Why]
Avoid unnecessary GPIO configuration attempts on dcn that doesn't
support it.

[How]
Conditionally use GPIO HPD detection or rely on hw encoder path.

Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Signed-off-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>