feat(linux): Add initial performance guide for AM62L 12.00.00 release

Add the initial Linux & RT Linux performance guide for 12.00.00 release
for AM62L.

Note that the following sections are still pending updates:
- ETHERNET
- OSPI
- LPM
- RT CYCLIC

Signed-off-by: Judith Mendez <jm@ti.com>

Author: jmenti