feat(handoff): add func to check and init a tl

Add a function to check whether a transfer list has been initialized
at the input address. If not, initialize a transfer list at the
specified location with the given size. This is to help ensure that we
don't accidently overwrite a transfer list that's been passed from a
previous stage.

Change-Id: Ic5906626df09d3801435488e258490765e8f81eb
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
2 files changed