selftest: fix build error in tools/testing/selftests/vm/userfaultfd.c

stable inclusion
from stable-5.10.56
commit e44d22fdf75613503b31a38fa824a98c970ea119
bugzilla: 176004 https://gitee.com/openeuler/kernel/issues/I4DYZ4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e44d22fdf75613503b31a38fa824a98c970ea119



--------------------------------

When backporting 0db282ba ("selftest: use mmap instead of
posix_memalign to allocate memory") to this stable branch, I forgot a {
breaking the build.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>