docs: mec15xxevb assy6853 updated sequence events

During the first real test of my manual by another developer,
I found out that it would be better to update sequence of events.
Also found out misprints, and some actions was not so obvious.
Corrected manual to be more green developers friendly.

Signed-off-by: Maksim Masalski <maksim.masalski@intel.com>