This reverts commit 79af7fbf4ef0185fa501e23a900a2ad933f845a7.
Because:
* btashton reported some issues in local builds:
https://github.com/apache/incubator-nuttx/pull/603#issuecomment-602264860
* this might be related to the current CI breakage:
> /bin/sh: 1: /__w/incubator-nuttx/incubator-nuttx/nuttx/tools/mkdeps: not found
Largely copy-and-paste from stm32f4discovery.
Also arch/arm/src/armv7-m/mpu.h: Ensure RBAR alignment
Fix crashes on init task startup I observed on qemu-system-arm -M lm3s6965evb.