xen/arm: copy dtb fragment to guest dtb

xen/arm: copy dtb fragment to guest dtb

Read the dtb fragment corresponding to a passthrough device from memory
at the location referred to by the "multiboot,device-tree" compatible
node.

Add a new field named dtb_bootmodule to struct kernel_info to keep track
of the dtb fragment location.

Copy the fragment to the guest dtb (only /aliases and /passthrough).

Set kinfo->phandle_gic based on the phandle of the special "/gic"
node in the device tree fragment. "/gic" is a dummy node in the dtb
fragment that represents the gic interrupt controller. Other properties
in the dtb fragment might refer to it (for instance interrupt-parent of
a device node). We reuse the phandle of "/gic" from the dtb fragment as
the phandle of the full GIC node that will be created for the guest
device tree. That way, when we copy properties from the device tree
fragment to the domU device tree the links remain unbroken.

scan_passthrough_prop is introduced here and not used in this patch but
it will be used by later patches.

Some of the code below is taken from tools/libxl/libxl_arm.c. Note that
it is OK to take LGPL 2.1 code and including it into a GPLv2 code base.
The result is GPLv2 code.

Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
Acked-by: Julien Grall <julien.grall@arm.com>
----
Changes in v6:
- code style
- in-code comment
- commit message improvements

Changes in v5:
- code style
- in-code comment
- remove depth parameter from scan_pfdt_node
- for instead of loop in domain_handle_dtb_bootmodule
- move "gic" check to domain_handle_dtb_bootmodule
- add check_partial_fdt
- use DT_ROOT_NODE_ADDR/SIZE_CELLS_DEFAULT
- add scan_passthrough_prop parameter, set it to false for "/aliases"

Changes in v4:
- use recursion in the implementation
- rename handle_properties to handle_prop_pfdt
- rename scan_pt_node to scan_pfdt_node
- pass kinfo to handle_properties
- use uint32_t instead of u32
- rename r to res
- add "passthrough" and "aliases" check
- add a name == NULL check
- code style
- move DTB fragment scanning earlier, before DomU GIC node creation
- set guest_phandle_gic based on "/gic"
- in-code comment

Changes in v3:
- switch to using device_tree_for_each_node for the copy

Changes in v2:
- add a note about the code coming from libxl in the commit message
- copy /aliases
- code style