powerpc: Fix section mismatch warning in free_lppacas

While cross-building for PPC64 I've got bunch of

WARNING: arch/powerpc/kernel/built-in.o(.text.unlikely+0x2d2): Section
mismatch in reference from the function .free_lppacas() to the variable
.init.data:lppaca_size The function .free_lppacas() references the variable
__initdata lppaca_size. This is often because .free_lppacas lacks a __initdata
annotation or the annotation of lppaca_size is wrong.

Fix it by using proper annotation for free_lppacas. Additionally, annotate
{allocate,new}_llpcas properly.

Signed-off-by: Vladimir Murzin <murzin.v@gmail.com>
Acked-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>