The use of static_call_cond() is essentially the same as static_call() on
x86 (e.g. static_call() now handles a NULL pointer as a NOP), and then the
kvm_x86_call() is added to improve code readability and maintainability
for keeping consistent code style.
Fixes 8d032b683c29 ("KVM: TDX: create/destroy VM structure")