drm/amd/powerplay: SCLK will have a big drop with low VDDC when PPlib was enabled.

SMC uses CurrSclkPllRange structure to keep track of what range of
PLL SCLK is sitting on.  Driver overwrites this value to 0 because
it's part of DPM table and driver doesn't program this.
This change will set this field to 0xFF every time there's a
init SMC table call.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>