via-pmu: Add compat_pmu_ioctl

The ioctls are actually compatible, but due to historical mistake the
numbers differ between 32bit and 64bit.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>