KVM: x86: Unconditionally set l1tf_flush_l1d during vCPU load

KVM: x86: Unconditionally set l1tf_flush_l1d during vCPU load

Always set l1tf_flush_l1d during kvm_arch_vcpu_load() instead of setting
it only when the vCPU is being scheduled back in.  The flag is processed
only when VM-Enter is imminent, and KVM obviously needs to load the vCPU
before VM-Enter, so attempting to precisely set l1tf_flush_l1d provides no
meaningful value.  I.e. the flag _will_ be set either way, it's simply a
matter of when.

Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240522014013.1672962-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>