tools/libs/ctrl: fix xc_core_arch_map_p2m() to support linear p2m table

tools/libs/ctrl: fix xc_core_arch_map_p2m() to support linear p2m table

The core of a pv linux guest produced via "xl dump-core" is nor usable
as since kernel 4.14 only the linear p2m table is kept if Xen indicates
it is supporting that. Unfortunately xc_core_arch_map_p2m() is still
supporting the 3-level p2m tree only.

Fix that by copying the functionality of map_p2m() from libxenguest to
libxenctrl.

Additionally the mapped p2m isn't of a fixed length now, so the
interface to the mapping functions needs to be adapted. In order not to
add even more parameters, expand struct domain_info_context and use a
pointer to that as a parameter.

Fixes: dc6d60937121 ("libxc: set flag for support of linear p2m list in domain builder")
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wl@xen.org>