drm/amdgpu: rename umc ras_init to err_cnt_init

this interface is related to specific version of umc, distinguish it
from ras_late_init

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>