drm/amd/display: Remove unused read_ono_state function from Hwss module

[Why]
The functions read_ono_state are no longer in use and have been identified
as redundant.
Removing them helps streamline the codebase and improve maintainability by
eliminating unnecessary code.

[How]
These unused functions were removed from Hwss module, ensuring that no
functionality is affected, and the code is simplified.

Reviewed-by: Martin Leung <martin.leung@amd.com>
Signed-off-by: Karthi Kandasamy <karthi.kandasamy@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>