Thermal: rename thermal_sys.c to thermal_core.c

this is the preparation work to build all the thermal core framework
source file, like governors, cpu cooling, etc, into one module.

No functional change in this patch.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Acked-by: Eduardo Valentin <eduardo.valentin@ti.com>
Acked-by: Durgadoss R <durgadoss.r@intel.com>

drivers/thermal/Makefile

@@ -3,6 +3,7 @@
 #
 
 obj-$(CONFIG_THERMAL)		+= thermal_sys.o
+thermal_sys-y			+= thermal_core.o
 
 # governors
 obj-$(CONFIG_THERMAL_GOV_FAIR_SHARE)	+= fair_share.o