KVM: Bump maximum vcpu count to 64

With slots_lock converted to rcu, the entire kvm hotpath on modern processors
(with npt or ept) now scales beautifully.  Increase the maximum vcpu count to
64 to reflect this.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -25,7 +25,7 @@
 #include <asm/mtrr.h>
 #include <asm/msr-index.h>
 
-#define KVM_MAX_VCPUS 16
+#define KVM_MAX_VCPUS 64
 #define KVM_MEMORY_SLOTS 32
 /* memory slots that does not exposed to userspace */
 #define KVM_PRIVATE_MEM_SLOTS 4