m7_defconfig: Disable CONFIG_STRICT_MEMORY_RWX
Its intention is to protect against theoretical vulnerabilities, but
in reality it opens the door for an already actively used exploit.
https://www.codeaurora.org/projects/security-advisories/configstrictmemoryrwx-not-strictly-enforced-cve-2013-4737
The security patch that fixes CONFIG_STRICT_MEMORY_RWX is expensive.
Better conserve the resources and protect us by simple disable of it.