Add function copy_dev_tables to copy the old DEV table entries of the panicked
kernel to the new allocated device table. Since all iommus share the same device
table the copy only need be done one time. Here add a new global old_dev_tbl_cpy
to point to the newly allocated device table which the content of old device
table will be copied to. Besides, we also need to:

  - Check whether all IOMMUs actually use the same device table with the same size

  - Verify that the size of the old device table is the expected size.

  - Reserve the old domain id occupied in 1st kernel to avoid touching the old
    io-page tables. Then on-flight DMA can continue looking it up.

And also define MACRO DEV_DOMID_MASK to replace magic number 0xffffULL, it can be
reused in copy_dev_tables().
Signed-off-by: NBaoquan He <bhe@redhat.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>