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

Link: https://lkml.kernel.org/r/20241010125323.3127187-1-ruanjinjie@huawei.com
Fixes: b8ee5575 ("mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>