v2: add Vega12 support

1. delete useless argument in function register_thermal_interrupt
2. rename function name register_thermal_interrupt to register_irq_handlers
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>