Fix aio_suspend in 32-bit emulation
An off-by-one error has been present since the system call was first present
in 185878. It additionally became a memory corruption bug after change
- The failure is actually revealed by our existing AIO tests.
However, apparently nobody's been running those in 32-bit emulation mode.
Reported by: Coverity, cem
CID: 1382114
MFC after: 18 days
X-MFC-With: 324941
Sponsored by: Spectra Logic Corp