drm/radeon: don't set default clocks for SI when DPM is disabled

drm/radeon: don't set default clocks for SI when DPM is disabled

commit 360991867d83e10827d907ef67206986a98953b3 upstream.

This is a partial revert of c6cf7777a32da874fabec4fd1c2a579f0ba4e4dd.

We need to take into account the clk voltage dependencies of the
board.  Not doing so can lead to stability issues on certain
boards if the clks exceed the levels in the dep tables.

DPM already takes that into account, so for optimal performance,
use DPM.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>