perf: Add initial Linux performance guide for am335x 11.02 release

Add the initial Linux performance guide for 11.02 release for
am335x device.

Note that the following sections are missing & will potentially be
added in subsequent PR:
- boot-time measurement
- alsa
- Graphics GLbenchmark
- IPSec Hardware Performance
- IPSec Software Performance

Signed-off-by: Judith Mendez <[email protected]>

Author: jmenti