KVM: x86: Add RIP to the kvm_entry, i.e. VM-Enter, tracepoint

Add RIP to the kvm_entry tracepoint to help debug if the kvm_exit
tracepoint is disabled or if VM-Enter fails, in which case the kvm_exit
tracepoint won't be hit.

Read RIP from within the tracepoint itself to avoid a potential VMREAD
and retpoline if the guest's RIP isn't available.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923201349.16097-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>