userfaultfd/selftests: use swap() instead of open coding it

Address the following coccicheck warning:

tools/testing/selftests/vm/userfaultfd.c:1536:21-22: WARNING opportunity
for swap().
tools/testing/selftests/vm/userfaultfd.c:1540:33-34: WARNING opportunity
for swap().

by using swap() for the swapping of variable values and drop
`tmp_area` that is not needed any more.

`swap()` macro in userfaultfd.c is introduced in commit 681696862bc18
("selftests: vm: remove dependecy from internal kernel macros")

It has been tested with gcc (Debian 8.3.0-6) 8.3.0.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Guo Zhengkui <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Reviewed-by: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions