xen: arm: handle concatenated root tables in dump_pt_walk

xen: arm: handle concatenated root tables in dump_pt_walk

ARM allows for the concatenation of pages at the root of a p2m (but not a
regular page table) in order to support a larger IPA space than the number of
levels in the P2M would normally support. We use this to support 40-bit guest
addresses.

Previously we were unable to dump IPAs which were outside the first page of the
root. To fix this we adjust dump_pt_walk to take the machine address of the
page table root instead of expecting the caller to have mapped it. This allows
the walker code to select the correct page to map.

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