drm/radeon: Clean up errors in si.c

Fix the following errors reported by checkpatch:

ERROR: that open brace { should be on the previous line
ERROR: trailing statements should be on next lineo

Signed-off-by: XueBing Chen <chenxb_99091@126.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>