cmd_bdinfo: display the address map size (32-bit vs. 36-bit)

Some Freescale SOCs support 32-bit and 36-bit physical addressing, and
U-Boot must be built to enable one or the other.  Add this information
to the bdinfo command.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>