io_uring: use force attribute for __kernel_rwf_t casts to make sparse happy

io_uring: use force attribute for __kernel_rwf_t casts to make sparse happy

Fixes sparse warnings:
fs/io_uring.c: note: in included file (through include/trace/perf.h,
include/trace/define_trace.h, include/trace/events/io_uring.h):
./include/trace/events/io_uring.h:488:1: sparse:
 warning: incorrect type in assignment (different base types)
    expected unsigned int [usertype] op_flags
    got restricted __kernel_rwf_t const [usertype] rw_flags
fs/io_uring.c:3164:23: sparse:
 warning: incorrect type in assignment (different base types)
    expected unsigned int [usertype] flags
    got restricted __kernel_rwf_t
fs/io_uring.c:3769:48: sparse:
 warning: incorrect type in argument 2 (different base types)
    expected restricted __kernel_rwf_t [usertype] flags
    got unsigned int [usertype] flags

__kernel_rwf_t type is bitwise and requires __force attribute for casts

Signed-off-by: Vasily Averin <vvs@openvz.org>
Link: https://lore.kernel.org/r/45e8576e-5fcc-bc52-8805-0b5cc3fc1a84@openvz.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>