drm/radeon: KV has three PPLLs (v2)

Enable all three in the driver.  Early documentation
indicated the 3rd one was used for something else, but
that is not the case.

v2: handle disable as well

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

diff --cc drivers/gpu/drm/radeon/atombios_crtc.c
Simple merge