v2: add Vega12 support

1. remove struct cgs_os_ops
2. delete cgs_linux.h
3. refine the irq code for vega10, can fix set pp table
   failed issue.
4. add common smu irq process function
Acked-by: NChristian König <christian.koenig@amd.com>
Acked-by: NJunwei Zhang <Jerry.Zhang@amd.com>
Signed-off-by: NRex Zhu <Rex.Zhu@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>