powerpc/tau: Remove superfluous parameter in alloc_workqueue() call

This avoids an (optional) compiler warning:

arch/powerpc/kernel/tau_6xx.c: In function 'TAU_init':
arch/powerpc/kernel/tau_6xx.c:204:30: error: too many arguments for format [-Werror=format-extra-args]
  tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);

Fixes: b1c6a0a1 ("powerpc/tau: Convert from timer to workqueue")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a1456e8bbd33ef702e3ff6f14b1bf3919241c62b.1623398307.git.fthain@linux-m68k.org