parisc: convert to generic helpers for IPI function calls

This converts parisc to use the new helpers for smp_call_function() and
friends, and adds support for smp_call_function_single(). Tested by
Kyle, seems to work.

Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>