Seems that it depends on if you installed Windows 10 by BIOS or EFI. For BIOS installed configurations you would have to disable SIP in order to use the bootcamp partition as a VM.
Hopefully VMware finds a better solution.
[0] https://communities.vmware.com/thread/572924
If it works out for you then buy and assign the license to the install and the time limit will be removed (so no need to reinstall)
[0] http://www.vmware.com/products/fusion/fusion-evaluation