drm/amd/pm: correct Vega20 swctf limit setting

commit 9b51c4b2ba31396f3894ccc7df8bdf067243e9f5 upstream.

Correct the Vega20 thermal swctf limit.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>