[PATCH 0/2][X] CVE-2017-18174 - Denial of service in AMD GPIO pin control

[Tyler Hicks]

https://people.canonical.com/~ubuntu-security/cve/?cve=CVE-2017-18174

 In the Linux kernel before 4.7, the amd_gpio_remove function in
 drivers/pinctrl/pinctrl-amd.c calls the pinctrl_unregister function,
 leading to a double free.

Clean cherry pick to Xenial. I had to incorporate a stray build failure fix
from a related patch. I'm unable to test these changes since it requires
specific AMD hardware. The build logs are clean and the changes are fairly
straightforward.

Tyler