parisc: disable preemption while flushing D- or I-caches through TMPALIAS region

It is necessary to disable preemption during cache flushes done through the
TMPALIAS region to ensure that the TLB setup is not clobbered by another flush.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>