ACPICA: Change an exception code for the ASL UnLoad() operator

Change the exception code for the case where the input DdbHandle
is invalid from AE_BAD_PARAMETER to the more appropriate
AE_AML_OPERAND_TYPE.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>