libata: improve HPA error handling

There's no point in retrying and eventually failing device detection
when the device rejects READ_NATIVE_MAX[_EXT].  Disable HPA unlocking
if READ_NATIVE_MAX[_EXT] is rejected as done when SET_MAX[_EXT] is
rejected.

This allows some old drives to work even if they aren't blacklisted.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>