powerpc: Fix compile error with paca code on ppc64e

arch/powerpc/kernel/paca.c: In function 'allocate_lppacas':
arch/powerpc/kernel/paca.c:111:1: error: parameter name omitted
arch/powerpc/kernel/paca.c:111:1: error: parameter name omitted

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>