[why]
With DSC power gating enabled, one of the register reads times out occasionally,
causing a DSC test to fail.

[how]
Disable DSC power gating in Diags.
NOTE: This has to be reverted once the problems with DSC power gating are
resolved.
Signed-off-by: NNikola Cornij <nikola.cornij@amd.com>
Reviewed-by: NNevenko Stupar <Nevenko.Stupar@amd.com>
Acked-by: NBhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>