xen/dts: Don't translate invalid address

xen/dts: Don't translate invalid address

ePAR specifies that if the property "ranges" doesn't exist in a bus node:

"it is assumed that no mapping exists between children of node and the parent
address space".

Modify dt_number_of_address to check if the list of ranges are valid. Return
0 (ie there is zero range) if the list is not valid.

This patch has been tested on the Arndale where the bug can occur with the
'/hdmi' node.

Reported-by: <tsahee@gmx.com>
Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>