isci: bypass scic_controller_get_handler_methods()

The indirection is unecessary and broken in the current case that assigns the
handlers based on a not up-to-date pdev->msix_enabled value.

Route the handlers directly to the requisite core routines.

Todo: hook up error interrupt handling

Reported-by: Jeff Garzik <jeff@garzik.org>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Edmund Nadolski <edmund.nadolski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>