Enable KVM on 64bit Builds

[macromorgan]

I would like to propose enabling KVM on the 64 bit builds. To my knowledge KVM is not available for 32bit ARM, so this would require a slight deviation in the kernels between 32 and 64 bit.

I'm using KVM currently in the existing kernel (provided by sakaki- from here: https://github.com/sakaki-/bcm2711-kernel-bis), but it would be great if I could use the actual foundation kernel which is maintained in apt for Raspbian.

[pelwell]

Essentially a duplicate of #3035 (but I think you know that).