Build: Remove support for Armclang version less than 6.10

This patch removes support for Armclang versions lower than
6.10. It updates documentation as well.

Change-Id: I71e2c0cba01cb1b9ec06734d89ec707319a3f78c
Signed-off-by: Antonio de Angelis <antonio.deangelis@arm.com>
3 files changed