isci: remove scic_controller_get_handler_methods and ilk

This removes scic_controller_get_handler_methods and its
associated unused code.

Signed-off-by: Edmund Nadolski <edmund.nadolski@intel.com>
[djbw: kill off the legacy handler, now that we have basic error isr support]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>