netdevsim: Fix memory leak of nsim_dev->fa_cookie

kmemleak reports this issue:

unreferenced object 0xffff8881bac872d0 (size 8):
  comm "sh", pid 58603, jiffies 4481524462 (age 68.065s)
  hex dump (first 8 bytes):
    04 00 00 00 de ad be ef                          ........
  backtrace:
    [<00000000c80b8577>] __kmalloc+0x49/0x150
    [<000000005292b8c6>] nsim_dev_trap_fa_cookie_write+0xc1/0x210 [netdevsim]
    [<0000000093d78e77>] full_proxy_write+0xf3/0x180
    [<000000005a662c16>] vfs_write+0x1c5/0xaf0
    [<000000007aabf84a>] ksys_write+0xed/0x1c0
    [<000000005f1d2e47>] do_syscall_64+0x3b/0x90
    [<000000006001c6ec>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

The issue occurs in the following scenarios:

nsim_dev_trap_fa_cookie_write()
  kmalloc() fa_cookie
  nsim_dev->fa_cookie = fa_cookie
..
nsim_drv_remove()

The fa_cookie allocked in nsim_dev_trap_fa_cookie_write() is not freed. To
fix, add kfree(nsim_dev->fa_cookie) to nsim_drv_remove().

Fixes: d3cbb907 ("netdevsim: add ACL trap reporting cookie as a metadata")
Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Cc: Jiri Pirko <jiri@mellanox.com>
Link: https://lore.kernel.org/r/1668504625-14698-1-git-send-email-wangyufen@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/netdevsim/dev.c

@@ -1683,6 +1683,7 @@ void nsim_drv_remove(struct nsim_bus_dev *nsim_bus_dev)
 				  ARRAY_SIZE(nsim_devlink_params));
 	devl_resources_unregister(devlink);
 	kfree(nsim_dev->vfconfigs);
+	kfree(nsim_dev->fa_cookie);
 	devl_unlock(devlink);
 	devlink_free(devlink);
 	dev_set_drvdata(&nsim_bus_dev->dev, NULL);