netdevsim: use IS_ERR instead of IS_ERR_OR_NULL for debugfs

Debugfs APIs return valid pointer or error pointer. it doesn't return NULL.
So, using IS_ERR is enough, not using IS_ERR_OR_NULL.

Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
3 files changed