drm/amd/display: Enable dpia support for dcn314

[Why]
DCN 3.1.4 supports DPIA.

[How]
 - Set dpia_supported flag for dcn314 in dmub_hw_init()
 - Remove comment that becomes irrelevant after this change.

Signed-off-by: Roman Li <roman.li@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 6.0.x