UBUNTU: SAUCE: [Fix] x86/KVM/VMX: Add L1D flush logic

UBUNTU: SAUCE: [Fix] x86/KVM/VMX: Add L1D flush logic

BugLink: https://bugs.launchpad.net/bugs/1822760
The backport of upstream commit c595ceee4570 ("x86/KVM/VMX: Add L1D flush
logic") incorrectly put the enabling of L1D flushing in
kvm_write_guest_virt_helper() instead of kvm_write_guest_virt_system().

Fixes: f0ace387064d ("x86/KVM/VMX: Add L1D flush logic")
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>