Microsoft has now started pushing a new update KB4073290 (Build 16299.194) for AMD devices on Windows 10 Fall Creators update. The Specter and Meltdown fixes that arrived with Build 16299.192 made AMD devices to fall into unbootable state.
This update that takes the Windows 10 Build to 10.0.16299.194 should be able to fix unbootable state issue.
Changelog:
An update is available to fix the following issue that occurs after you install January 3, 2018—KB4056892 (OS Build 16299.192):
AMD devices fall into an unbootable state.
How to download:
To get the stand-alone package for this update click on the below link
 fixes Unbootable state for AMD devices in Fall Creators update (Version 1709). Download link){kind=link}