drm/amdgpu/ci: disable mclk switching for high refresh rates (v2)

drm/amdgpu/ci: disable mclk switching for high refresh rates (v2)

BugLink: http://bugs.launchpad.net/bugs/1698799
commit 0a646f331db0eb9efc8d3a95a44872036d441d58 upstream.

Even if the vblank period would allow it, it still seems to
be problematic on some cards.

v2: fix logic inversion (Nils)

bug: https://bugs.freedesktop.org/show_bug.cgi?id=96868

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>