MAINTAINERS: update io_uring entry

We now have a list that's appropriate for both kernel and userspace
discussions on io_uring usage and development, add that to the
MAINTAINERS entry.

Also add the io-wq files.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

MAINTAINERS

@@ -8562,12 +8562,13 @@ F:	include/linux/iova.h
 
 IO_URING
 M:	Jens Axboe <axboe@kernel.dk>
-L:	linux-block@vger.kernel.org
-L:	linux-fsdevel@vger.kernel.org
+L:	io-uring@vger.kernel.org
 T:	git git://git.kernel.dk/linux-block
 T:	git git://git.kernel.dk/liburing
 S:	Maintained
 F:	fs/io_uring.c
+F:	fs/io-wq.c
+F:	fs/io-wq.h
 F:	include/uapi/linux/io_uring.h
 
 IPMI SUBSYSTEM