misc: Fix possible use-before-initialization errors

All of these issues stem from assuming that passing a pointer-to-mutable
will initialize the object if it's not already initialized, but it's
unsafe to assume this is the case even if it is judged that the call
returned successfully, as the implementation may change at any point.

Change-Id: Ica114514429005b18d04efce2529e0a64a182525
Signed-off-by: Chris Kay <chris.kay@arm.com>