list: test: increase coverage of list_test_list_replace*()

list: test: increase coverage of list_test_list_replace*()

Increase the test coverage of list_test_list_replace*() by adding the
checks to compare the pointer of "a_new.next" and "a_new.prev" to make
sure a perfect circular doubly linked list is formed after the
replacement.

Link: https://lkml.kernel.org/r/20240910040818.65723-1-richard120310@gmail.com
Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
Cc: David Gow <davidgow@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>