ACPI / util: remove redundant check if element is NULL

element is &package->package.elements[i] which can never be NULL
so the check to see if it is NULL is redundant and can be removed.

Detected with static analysis by CoverityScan

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>