Change bd/gd memsize/ram_size to be phys_size_t.

Currently, both are defined as an unsigned long, but
should be phys_size_t. This should result in no real change,
since phys_size_t is currently an unsigned long for all the
default configs.  Also add print_lnum to cmd_bdinfo to deal
with the potentially wider memsize.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>