KVM: nVMX: Advertise support for MSR_IA32_VMX_TRUE_*_CTLS

We already implemented them but failed to advertise them. Currently they
all return the identical values to the capability MSRs they are
augmenting. So there is no change in exposed features yet.

Drop related comments at this chance that are partially incorrect and
redundant anyway.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>