KVM: x86: remove WARN_ON from get_kernel_ns()

Function and callers can be preempted.

https://bugzilla.kernel.org/show_bug.cgi?id=73721

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -1123,7 +1123,6 @@ static inline u64 get_kernel_ns(void)
 {
 	struct timespec ts;
 
-	WARN_ON(preemptible());
 	ktime_get_ts(&ts);
 	monotonic_to_bootbased(&ts);
 	return timespec_to_ns(&ts);