KVM: selftests: Remove superfluous variable assignment

Don't nullify "nodep" to NULL one line before it's set to "tmp".

Signed-off-by: Minjie Du <duminjie@vivo.com>
Link: https://lore.kernel.org/r/20230704122148.11573-1-duminjie@vivo.com


[sean: massage shortlog+changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>