drm/radeon/kms: add support for internal thermal sensors (v3)

rv6xx/rv7xx/evergreen families supported; older asics did
not have an internal thermal sensor.

Note, not all oems use the internal thermal sensor, so it's
only exposed in cases where it is used.

Note also, that most laptops use an oem specific ACPI solution for
GPU thermal information rather than using the internal thermal
sensor directly.

v2: export millidegrees celsius, use hwmon device properly.
v3: fix Kconfig

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/evergreend.h

@@ -165,6 +165,11 @@
 #define		SE_DB_BUSY					(1 << 30)
 #define		SE_CB_BUSY					(1 << 31)
 
+#define	CG_MULT_THERMAL_STATUS				0x740
+#define		ASIC_T(x)			        ((x) << 16)
+#define		ASIC_T_MASK			        0x7FF0000
+#define		ASIC_T_SHIFT			        16
+
 #define	HDP_HOST_PATH_CNTL				0x2C00
 #define	HDP_NONSURFACE_BASE				0x2C04
 #define	HDP_NONSURFACE_INFO				0x2C08