mem_event: remove type member

mem_event: remove type member

When mem_event was added the type flag should indicate who the consumer
is. But the concept of a single ring buffer for multiple event types can
not work for two reasons. One is that no multiplexer exists which
provides individual event types to the final consumer, and second is
that even if such multiplexer can not work reliable because a request
needs to be answered with a response. The response should be sent
roughly in the order of received events. But with multiple consumers one
of them can so stall all the others.

For that reason the single mem_event buffer for all types of events was
split into individual ring buffers with commit 23842:483c5f8319ad. This
commit made the type member already obsolete because the meaning of each
buffer is now obvious.

This change removes the type member and increases the flags field.

Even though this is an ABI incompatible change, it will have no practical
impact on existing binaries because the changeset referenced above already
bumped the SONAME. So these binaries have to be recompiled anyway for the
upcoming major release.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>