convert buf-ring nop test to use read
convert buf-ring nop test to use read

The NOP support for IOSQE_BUFFER_SELECT has been reverted, so use a
supported function with read. This also allows verifying that the
correct data has actually been read.

Signed-off-by: Dylan Yudaken <203ae8bb785c49229d9d2ff72bddc0c8f3aba6ea@fb.com>
Link: https://lore.kernel.org/r/20220615113733.1424472-1-203ae8bb785c49229d9d2ff72bddc0c8f3aba6ea@fb.com
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing