io: Fix record locking contants for powerpc64 with __USE_FILE_OFFSET64

Commit 5f828ff8 ("io: Fix F_GETLK, F_SETLK, and F_SETLKW for
powerpc64") fixed an issue with the value of the lock constants on
powerpc64 when not using __USE_FILE_OFFSET64, but it ended-up also
changing the value when using __USE_FILE_OFFSET64 causing an API change.

Fix that by also checking that define, restoring the pre
4d0fe291 commit values:

Default values:
- F_GETLK: 5
- F_SETLK: 6
- F_SETLKW: 7

With -D_FILE_OFFSET_BITS=64:
- F_GETLK: 12
- F_SETLK: 13
- F_SETLKW: 14

At the same time, it has been noticed that there was no test for io lock
with __USE_FILE_OFFSET64, so just add one.

Tested on x86_64-linux-gnu, i686-linux-gnu and
powerpc64le-unknown-linux-gnu.

Resolves: BZ #30804.
Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
(cherry picked from commit 434bf72a)