drm/amd/display: Initialize replay_config var

[Why]
Uninitialized variables could cause some bits to be set, thus enabling
features unintentionally.

[How]
Initialize replay_config variable to avoid future issues.

Reviewed-by: Harry Vanzylldejong <harry.vanzylldejong@amd.com>
Reviewed-by: Iswara Nagulendran <iswara.nagulendran@amd.com>
Reviewed-by: Anthony Koo <anthony.koo@amd.com>
Signed-off-by: Kaitlyn Tse <Kaitlyn.Tse@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>