stat-util: rename files_same() → inode_same()

Let's be more accurate about what this function does: it checks whether
the underlying reported inode is the same. Internally, this already uses
a better named stat_inode_same() call, hence let's similarly name the
wrapping function following the same logic.

Similar for files_same_at() and path_equal_or_same_files().

No code changes, just some renaming.

src/basic/path-util.c

@@ -485,8 +485,8 @@ int path_compare(const char *a, const char *b) {
         }
 }
 
-bool path_equal_or_files_same(const char *a, const char *b, int flags) {
-        return path_equal(a, b) || files_same(a, b, flags) > 0;
+bool path_equal_or_inode_same(const char *a, const char *b, int flags) {
+        return path_equal(a, b) || inode_same(a, b, flags) > 0;
 }
 
 int path_compare_filename(const char *a, const char *b) {