change some "rbca" to "rcrb"(root complex register block) while
the other to "rcba"(root complex base address).
Bonus: add more comments and fix some indentation.
Signed-off-by: NCao jin <caoj.fnst@cn.fujitsu.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>