display: remove compile time warnings

- remove unused variable in libexternal.
- make use of all variables in memtrack.

[haggertk: Picked to 8974. libexternal is N/A our family]

Change-Id: I67b34428f4a976327e4e9dcd6fd7dfb9063b969c
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
1 file changed