Spread spectrum seems to cause hangs when dynamic clock
switching is enabled.  Disable it for now. This does not
affect performance or the amount of power saved. Tracked
down by Martin Andersson.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=69723Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org