drm/amdgpu: define ras_reset_error_count function

Make the code architecture more simple.

v2: reuse ras_reset_error_count in ras_reset_error_status.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>