linux-yocto/5.15: cfg/xen: Move x86 configs to separate file

Integrating the following commit(s) to linux-yocto/.:

    ad633e22764 features/xen: Move x86 configs to separate file

Signed-off-by: Kamil Dziezyk <kamil.dziezyk@arm.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit a1362270)
Signed-off-by: Steve Sakoman <steve@sakoman.com>