docs: update Measured Boot PoC

Updated the Measured Boot PoC to be compliant with the current TF-A
implementation that supports multiple Measured Boot backends, which
are the RSS and Event Log.

Change-Id: I8a38a801dd75e6282d103e154966959bba2d1ec7
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
1 file changed