ACPICA: Fixed a couple of warnings under MSVC

ACPICA commit 86c919d2bad08491fc91ffa53e9b169092de8622

Repaired with casts.

Link: https://github.com/acpica/acpica/commit/86c919d2


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