drm/radeon/kms/ni: load default sclk/mclk/vddc at pm init

The vbios only partially initializes the memory controller on
NI, so now we need to load the MC ucode in the driver and set
the default clocks once the ucode is loaded.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>