mm/damon/tests/sysfs-kunit.h: fix memory leak in damon_sysfs_test_add_targets()

In the Linux kernel, the following vulnerability has been resolved:

mm/damon/tests/sysfs-kunit.h: fix memory leak in damon_sysfs_test_add_targets()

The sysfs_target->regions allocated in damon_sysfs_regions_alloc() is not freed in damon_sysfs_test_add_targets(), which cause the following memory leak, free it to fix it.

unreferenced object 0xffffff80c2a8db80 (size 96): comm "kunit_try_catch", pid 187, jiffies 4294894363 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 0): [<0000000001e3714d>] kmemleak_alloc+0x34/0x40 [<000000008e6835c1>] __kmalloc_cache_noprof+0x26c/0x2f4 [<000000001286d9f8>] damon_sysfs_test_add_targets+0x1cc/0x738 [<0000000032ef8f77>] kunit_try_run_case+0x13c/0x3ac [<00000000f3edea23>] kunit_generic_run_threadfn_adapter+0x80/0xec [<00000000adf936cf>] kthread+0x2e8/0x374 [<0000000041bb1628>] ret_from_fork+0x10/0x20