io_uring/rw: mark readv/writev as vectored in the opcode definition

This is cleaner than gating on the opcode type, particularly as more
read/write type opcodes may be added.

Then we can use that for the data import, and for __io_read() on
whether or not we need to copy state.

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

io_uring/opdef.c

@@ -63,6 +63,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.ioprio			= 1,
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
+		.vectored		= 1,
 		.prep			= io_prep_rw,
 		.issue			= io_read,
 	},
@@ -76,6 +77,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.ioprio			= 1,
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
+		.vectored		= 1,
 		.prep			= io_prep_rw,
 		.issue			= io_write,
 	},