tools/libxl_arm: Modify libxl__prepare_dtb...

tools/libxl_arm: Modify libxl__prepare_dtb...

... to take a second argument of type libxl_domain_config*
rather than libxl_domain_build_info*.

This change will be needed to get access from
libxl__prepare_dtb to "num_pcidevs" field of
libxl_domain_config to check whether to create
a vPCI DT node or not.

Signed-off-by: Michal Orzel <michal.orzel@arm.com>
Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
Suggested-by: Ian Jackson <iwj@xenproject.org>
Reviewed-by: Ian Jackson <iwj@xenproject.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>