MAINTAINERS: add xen config fragments to XEN HYPERVISOR sections

Make changes to the xen config fragments reach the XEN HYPERVISOR
maintainers and mailing list.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220810050712.9539-5-lukas.bulwahn@gmail.comSigned-off-by: Juergen Gross <jgross@suse.com>

MAINTAINERS

@@ -21906,12 +21906,14 @@ F:	drivers/*/xen-*front.c
 F:	drivers/xen/
 F:	include/uapi/xen/
 F:	include/xen/
+F:	kernel/configs/xen.config
 
 XEN HYPERVISOR X86
 M:	Juergen Gross <jgross@suse.com>
 R:	Boris Ostrovsky <boris.ostrovsky@oracle.com>
 L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
 S:	Supported
+F:	arch/x86/configs/xen.config
 F:	arch/x86/include/asm/pvclock-abi.h
 F:	arch/x86/include/asm/xen/
 F:	arch/x86/platform/pvh/