refactor(build): minor updates

Move RME to 9.2 optional features and add minor updates to comments.

Change-Id: I12a4940e82ca5df72af5421ddab43bc6a1628e95
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
(cherry picked from commit 3dafd960d4dbcb155e5825af2d761c9f0fcb1f53)
1 file changed