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>

tools/testing/selftests/kvm/lib/sparsebit.c

@@ -634,7 +634,6 @@ static void node_reduce(struct sparsebit *s, struct node *nodep)
 				tmp = node_prev(s, nodep);
 
 			node_rm(s, nodep);
-			nodep = NULL;
 
 			nodep = tmp;
 			reduction_performed = true;