imx6-tqma6: Convert to OF_UPSTREAM

Instead of using the local imx6-tqma6 devicetree copies from U-Boot,
convert the imx6-tqma6 target to OF_UPSTREAM so that the upstream
kernel devicetrees can be used instead.

Signed-off-by: Fabio Estevam <festevam@denx.de>
diff --git a/configs/tqma6dl_mba6_mmc_defconfig b/configs/tqma6dl_mba6_mmc_defconfig
index 1534a2e..be891d2 100644
--- a/configs/tqma6dl_mba6_mmc_defconfig
+++ b/configs/tqma6dl_mba6_mmc_defconfig
@@ -7,7 +7,7 @@
 CONFIG_ENV_OFFSET=0x100000
 CONFIG_MX6DL=y
 CONFIG_TARGET_TQMA6=y
-CONFIG_DEFAULT_DEVICE_TREE="imx6dl-mba6b"
+CONFIG_DEFAULT_DEVICE_TREE="nxp/imx/imx6dl-mba6b"
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_SUPPORT_RAW_INITRD=y