xen/device-tree: Print the DT path on error in dt_for_each_range

xen/device-tree: Print the DT path on error in dt_for_each_range

With the current log is not possible for the user to understand
properly the error:

(XEN) Grant table range: 0x0000007fc00000-0x0000007fc72000
(XEN) DT: no ranges; cannot enumerate
(XEN) Device tree generation failed (-22).
(XEN)
(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Could not set up DOM0 guest OS
(XEN) ****************************************
(XEN)

The other error message within the function already print the DT path.
Do the same here.

Signed-off-by: Julien Grall <julien.grall@citrix.com>