xen: Add essential and required interface headers

Add essential and required Xen interface headers only taken from
the stable Linux kernel stable/linux-5.7.y at commit
66dfe4522160 Linux 5.7.5.

These are better suited for U-boot than the original headers
from Xen as they are the stripped versions of the same.

At the same time use public protocols from Xen RELEASE-4.13.1, at
commit 6278553325a9 update Xen version to 4.13.1
as those have more comments in them.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
Acked-by: Peng Fan <peng.fan@nxp.com>