dm: mx6: sabre: Move driver model CONFIGs to Kconfig

Remove driver model CONFIGs from the board config headers and use Kconfig
instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/mx6sabresd_spl_defconfig b/configs/mx6sabresd_spl_defconfig
index 12e7844..67079ba 100644
--- a/configs/mx6sabresd_spl_defconfig
+++ b/configs/mx6sabresd_spl_defconfig
@@ -2,4 +2,5 @@
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg,SPL,MX6Q"
 +S:CONFIG_ARM=y
 +S:CONFIG_TARGET_MX6SABRESD=y
-
+CONFIG_DM=y
+CONFIG_DM_THERMAL=y