LoongArch: Fix debugfs_create_dir() error checking

LoongArch: Fix debugfs_create_dir() error checking

commit 41efbb682de1231c3f6361039f46ad149e3ff5b9 upstream.

The debugfs_create_dir() returns ERR_PTR in case of an error and the
correct way of checking it is using the IS_ERR_OR_NULL inline function
rather than the simple null comparision. This patch fixes the issue.

Cc: stable@vger.kernel.org
Suggested-By: Ivan Orlov <ivan.orlov0322@gmail.com>
Signed-off-by: Immad Mir <mirimmad17@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>