ACPI: Don't treat generic error as ACPI error code in acpi memory hotplug driver

Don't treat the generic error as ACPI error code. Otherwise when the generic
code is returned, it will complain the following warning messag:
   >ACPI Exception (acpi_memhotplug-0171): UNKNOWN_STATUS_CODE,
		Cannot get acpi bus device [20080609]
   >ACPI: Cannot find driver data
   > ACPI Error (utglobal-0127): Unknown exception code: 0xFFFFFFED [20080609]
   > Pid: 85, comm: kacpi_notify Not tainted 2.6.27.19-5-default #1
     Call Trace:
     [<ffffffff8020da29>] show_trace_log_lvl+0x41/0x58
     [<ffffffff8049a3da>] dump_stack+0x69/0x6f
    .....

At the same time when the generic error code is returned, the ACPI_EXCEPTION
is replaced by the printk.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>