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/mx6qsabresd_defconfig b/configs/mx6qsabresd_defconfig
index 09b0190..112918b 100644
--- a/configs/mx6qsabresd_defconfig
+++ b/configs/mx6qsabresd_defconfig
@@ -3,3 +3,5 @@
 CONFIG_TARGET_MX6SABRESD=y
 CONFIG_SYS_MALLOC_F=y
 CONFIG_SYS_MALLOC_F_LEN=0x400
+CONFIG_DM=y
+CONFIG_DM_THERMAL=y