parisc: implement irq stacks

parisc: implement irq stacks

commit 200c880420a2c02a0899120ce52d801fad705b90 upstream.

Default kernel stack size on parisc is 16k.  During tests we found that the
kernel stack can easily grow beyond 13k, which leaves 3k left for irq
processing.

This patch adds the possibility to activate an additional stack of 16k per CPU
which is being used during irq processing.  This implementation does not yet
uses this irq stack for the irq bh handler.

The assembler code for call_on_stack was heavily cleaned up by John
David Anglin.

Signed-off-by: Helge Deller <deller@gmx.de>
CC: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>