Make the tracing formatting for user_data and flags consistent.

Having consistent formatting allows one for example to grep for a specific
user_data/flags and be able to trace a single sqe through easily.

Change user_data to 0x%llx and flags to 0x%x everywhere. The '0x' is
useful to disambiguate for example "user_data 100".

Additionally remove the '=' for flags in io_uring_req_failed, again for consistency.
Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220316095204.2191498-1-dylany@fb.comSigned-off-by: Jens Axboe <axboe@kernel.dk>