DM: thermal: Add imx thermal DM driver

Add a new thermal uclass for thermal sensor and implement the imx
thermal driver basing on this uclass.

Signed-off-by: Ye.Li <B37916@freescale.com>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/drivers/Makefile b/drivers/Makefile
index 33227c8..7683c61 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -21,3 +21,4 @@
 obj-y += input/
 # SOC specific infrastructure drivers.
 obj-y += soc/
+obj-y += thermal/