parisc: clear floating point exception flag on SIGFPE signal

Clear the floating point exception flag before returning to
user space. This is needed, else the libc trampoline handler
may hit the same SIGFPE again while building up a trampoline
to a signal handler.

Fixes debian bug #559406.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>