drm/amd/pm: Clean up errors in vega12_hwmgr.c

Fix the following errors reported by checkpatch:

ERROR: need consistent spacing around '/' (ctx:WxV)
ERROR: code indent should use tabs where possible

Signed-off-by: Ran Sun <sunran001@208suo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>