drm/msm/sde: mitigate error log on disabling DSC

Encoder need to disable DSC when it shuts down or on seemless
mode switch. Handle the disable sequence only for DSC without
unnecessary logging for non-DSC topologies as it is valid to
switch from a non-DSC topology.

Change-Id: Iafd598b0a0c25a58ea94c1158077b4015824ce14
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>