qemu-char: Register ring buffer driver with correct name "ringbuf"

qemu-char: Register ring buffer driver with correct name "ringbuf"

The driver is new in 1.4, with the documented name "ringbuf".
However, it's actual name is the completely undocumented "memory".
Screwed up in commit 3949e59.  Fix code to match documentation.

Keep the undocumented name working as an alias for compatibility.

Cc: qemu-stable@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 1374849874-25531-3-git-send-email-armbru@redhat.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit c11ed9666d69abaf217c8800f299c519b487b7d3)

Conflicts:

	qemu-char.c

* removed dependency on command-line specifiable mux (bb6fb7c0)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>