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/mx6qsabrelite_defconfig b/configs/mx6qsabrelite_defconfig
index dfa9c2e..50b75ae 100644
--- a/configs/mx6qsabrelite_defconfig
+++ b/configs/mx6qsabrelite_defconfig
@@ -1,3 +1,5 @@
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6q.cfg,MX6Q,DDR_MB=1024,SABRELITE"
 CONFIG_ARM=y
 CONFIG_TARGET_NITROGEN6X=y
+CONFIG_DM=y
+CONFIG_DM_THERMAL=y