drm/radeon: add support for thermal sensor on tn

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/ni.c b/drivers/gpu/drm/radeon/ni.c
index 8458330..f889461 100644
--- a/drivers/gpu/drm/radeon/ni.c
+++ b/drivers/gpu/drm/radeon/ni.c
@@ -692,6 +692,14 @@
 	return err;
 }
 
+int tn_get_temp(struct radeon_device *rdev)
+{
+	u32 temp = RREG32_SMC(TN_CURRENT_GNB_TEMP) & 0x7ff;
+	int actual_temp = (temp / 8) - 49;
+
+	return actual_temp * 1000;
+}
+
 /*
  * Core functions
  */