KVM: VMX: Fix stale docs for kvm-intel.emulate_invalid_guest_state

Update the documentation for kvm-intel's emulate_invalid_guest_state to
rectify the description of KVM's default behavior, and to document that
the behavior and thus parameter only applies to L1.

Fixes: a27685c3 ("KVM: VMX: Emulate invalid guest state by default")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211207193006.120997-4-seanjc@google.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/admin-guide/kernel-parameters.txt

@@ -2413,8 +2413,12 @@
 			Default is 1 (enabled)
 
 	kvm-intel.emulate_invalid_guest_state=
-			[KVM,Intel] Enable emulation of invalid guest states
-			Default is 0 (disabled)
+			[KVM,Intel] Disable emulation of invalid guest state.
+			Ignored if kvm-intel.enable_unrestricted_guest=1, as
+			guest state is never invalid for unrestricted guests.
+			This param doesn't apply to nested guests (L2), as KVM
+			never emulates invalid L2 guest state.
+			Default is 1 (enabled)
 
 	kvm-intel.flexpriority=
 			[KVM,Intel] Disable FlexPriority feature (TPR shadow).