libata: remove functions now handed by ACPI dock driver

dock driver can handle ata(bay) hotplug now. dock driver already handles
_EJ0 and _STA, so remove them. Also libata doesn't need register
notification handler anymore.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>