After "linux-user: use target_ulong" the poll syscall was no longer
handling infinite timeout.
/home/abuild/rpmbuild/BUILD/qemu-2.7.0-rc5/linux-user/syscall.c:9773:26: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
if (arg3 >= 0) {
^~
Signed-off-by: Andreas Schwab <schwab@suse.de>