selftests/landlock: remove ARRAY_SIZE define from common.h

ARRAY_SIZE is defined in several selftests. Remove definitions from
individual test files and include header file for the define instead.
ARRAY_SIZE define is added in a separate patch to prepare for this
change.

Remove ARRAY_SIZE from common.h and pickup the one defined in
kselftest.h.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: shuahkh

tools/testing/selftests/landlock/common.h

@@ -17,10 +17,6 @@
 
 #include "../kselftest_harness.h"
 
-#ifndef ARRAY_SIZE
-#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
-#endif
-
 /*
  * TEST_F_FORK() is useful when a test drop privileges but the corresponding
  * FIXTURE_TEARDOWN() requires them (e.g. to remove files from a directory