io_uring: track restrictions separately for IORING_OP and IORING_REGISTER

io_uring: track restrictions separately for IORING_OP and IORING_REGISTER

It's quite likely that only register opcode restrictions exists, in
which case we'd never need to check the normal opcodes. Split
ctx->restricted into two separate fields, one for I/O opcodes, and one
for register opcodes.

Reviewed-by: Gabriel Krisman Bertazi <krisman@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>