mknodat/mknodat02.c: add ELOOP and EROFS error value test

And create mknodat.h to encapsulate mknodat syscall.

Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
syscalls/mknodat01: Fixes.

* Cleanup

* Use tst_exit() instead of return 0
  (the test failure wasn't propagated out at all!)

* Make use of tst_tmpdir()

* Fix test iterations with -i

* Fix dir permissions (fixes test failure)

  the positive testcase was failing because the test had not
  search permission on the directory pointed to by dirfd

* Fix typo in mkdirat01.c (misspelled name)

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>