liburing/test: fix build errors

Fix the following errors when make:
  error: ‘for’ loop initial declarations are only allowed in C99 mode
  error: redeclaration of ‘i’ with no linkage

Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2 files changed