parisc: Panic immediately when panic_on_oops

PA-RISC wants to sleep 5 seconds before panicking when panic_on_oops
is set, with no apparent reason. Remove this feature, since some users
may want their systems to fail as quickly as possible.

Users who want to delay reboot after panic can use PANIC_TIMEOUT.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Helge Deller <deller@gmx.de>