[LTP] [PATCH v3] syscalls/mmap15: Rewrite test using new LTP API

[Petr Vorel]

Hi Avinesh,

I'm sorry v3 come too late, although Cyril pointed out not needed needs_root and
else if => if change, in the end v2 was merged.

Thus I fixed this as a separate change.

Kind regards,
Petr