perf script: Add script to collect and display IBS samples

perf script: Add script to collect and display IBS samples

This patch adds a script to collect and display IBS samples.
There are the following options:

 perf script ibs [ibs_op|ibs_fetch] [-c period] <command>

Examples for usage:

 perf script ibs ibs_op <command>
 perf script ibs ibs_fetch <command>
 perf script record ibs ibs_op -c 500000 <command>
 perf script report ibs
 perf script record ibs ibs_op -c 500000 <command> | perf script report ibs

Signed-off-by: Robert Richter <robert.richter@amd.com>