parisc: Fix extraction of hash lock bits in syscall.S

The extru instruction leaves the most significant 32 bits of the target
register in an undefined state on PA 2.0 systems. If any of these bits
are nonzero, this will break the calculation of the lock pointer.

Fix by using extrd,u instruction via extru_safe macro on 64-bit kernels.

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