colibri_imx7: use device-tree for MTD partitions

Use device-tree fixup to communicate the MTD partitions to the
kernel. Remove mtdparts from the kernel command line.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/configs/colibri_imx7_defconfig b/configs/colibri_imx7_defconfig
index 2d75b27..ce60056 100644
--- a/configs/colibri_imx7_defconfig
+++ b/configs/colibri_imx7_defconfig
@@ -55,3 +55,4 @@
 CONFIG_G_DNL_VENDOR_NUM=0x1b67
 CONFIG_G_DNL_PRODUCT_NUM=0x4000
 CONFIG_OF_LIBFDT_OVERLAY=y
+CONFIG_FDT_FIXUP_PARTITIONS=y