docs(lfa): update porting guide with LFA platform APIs

Add details about the LFA platform APIs to the porting guide,
providing guidance on their usage and integration.

Change-Id: I3888c88ac649342172332b02b3e685df1e833b97
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
1 file changed