MLBEDSW-10754: Make kernel object usage more consistent
This commit rationalises the use of the kernel object to
make it simpler to use the unit kernel, and ensures that
called functions have the correct kernel constness to
prevent accidental modification.
Signed-off-by:
Philip Hall <philip.hall@arm.com>
Change-Id: I27c63feb8e876f359b434a916bed50f41c97f411