backport patch to fix TSC scaling for SVM

backport patch to fix TSC scaling for SVM

The following issue reported on the community forum [0] is likely
fixed by this.

In my case, loading a VM snapshot that originally was taken on an
Intel CPU on my AMD-based host often caused problems in other VMs. In
particular, it often led to CPU stalls, and sometimes clock jumps far
into the future. With this backport applied, everything seems to run
smoothly even after loading the "bad" snapshot 10 times.

The backport from upstream commit 11d39e8cc43e ("KVM: SVM: fix tsc
scaling cache logic consisted of dropping the parts for nested TSC
scaling, which is not yet present in our kernel, renaming the constant
for the default ratio, and some context changes.

[0] https://forum.proxmox.com/threads/112756/

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>