drm/amd/powerplay: Remove the SOC floor voltage setting

Remove W/A carried over from VG10 to set VDDSOC Floor Voltage
prior to enabling DPM since the VBIOS covers the floor voltage
setting now

Signed-off-by: Kenneth Feng <kenneth.feng@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>