ACPICA: More Clang changes

ACPICA commit 54b3aefb5de860306951c8c3339b1c37dcdf1b39

V8.0.1: Fixed all "dead assignment" warnings.

Link: https://github.com/acpica/acpica/commit/54b3aefb


Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>