ACPI: EC: fix use-after-free

This patch fixes a use-after-free introduced by
commit 30c08574


(ACPI: EC: Add new query handler to list head)

Spotted by the Coverity checker.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>