drm/radeon/ci_dpm: Remove redundant initialization of variables hi_sidd, lo_sidd

The variables hi_sidd and lo_sidd are being initialized with a values
that are never read, they are being updated later on. The assignments
are redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>