KVM: VMX: Include architectural defs header in capabilities.h

The capabilities header depends on asm/vmx.h but doesn't explicitly
include said file.  This currently doesn't cause problems as all users
of capbilities.h first include asm/vmx.h, but the issue often results in
build errors if someone starts moving things around the VMX files.

Fixes: 3077c19 ("KVM: VMX: Move capabilities structs and helpers to dedicated file")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/capabilities.h

@@ -2,6 +2,8 @@
 #ifndef __KVM_X86_VMX_CAPS_H
 #define __KVM_X86_VMX_CAPS_H
 
+#include <asm/vmx.h>
+
 #include "lapic.h"
 
 extern bool __read_mostly enable_vpid;