scripts: add a script to report RAM/ROM usage

Still WIP. Give statistics on memory/flash usage.

Run:
 make BOARD=<board> ram_report
 or
 make BOARD=<board> rom_report

Change-Id: I6b0aee09b89275e12f1cde863d2c0f5b8dfd0409
Signed-off-by: Anas Nashif <anas.nashif@intel.com>