feat(handoff): make tl generation flexible

Make the process of compiling a TL from DT source flexible. Provide a
top level recipe to make it easier for developers to build a transfer
list. Clean up integration of TLC into the build system.

Change-Id: I4466e27a457dfd5bf709dc3a360a2b63bf6030ce
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
5 files changed