docs: fix vhost-user protocol doc

docs: fix vhost-user protocol doc

Some editorial tweaks to the doc:

Add a ref link to Memory region description and Multiple Memory region
description.

Descriptions about memory regions are merged into one line.

Add extra type(64 bits) to Log description structure fields

Fix ’s to 's

Signed-off-by: luzhixing12345 <luzhixing12345@gmail.com>
Message-Id: <20240911060400.3472-1-luzhixing12345@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>