scripts: poll_system.sh: initial version

poll_system.sh is a script that helps to monitor interrupt
and system memory usage. Each poll is approximatly 1s in gap.

The script usage as follow:

 poll_system.sh --help|-h   :- to display usage info
 poll_system.sh -p <#>      :- to poll system info for # of times

The script automatically saves the information under
system_summary.txt

Signed-off-by: Ong Boon Leong <elvinongbl@gmail.com>