cmd: bdinfo: Map fdt_blob and new_fdt to sysmem

Map fdt_blob and new_fdt to sysmem, otherwise $fdtcontroladdr
and bdinfo output do not match and the bdinfo output address
is not a valid address accessible via sandbox memory accessors.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Simon Glass <sjg@chromium.org>