drm/amd/display: Only log during optimize_bandwidth call

Prevent logs during a prepare_bandwidth call to ensure log accuracy.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Acked-by: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Ethan Bitnun <etbitnun@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>