padata: Section cleanup

This patch removes the __cupinit from padata_cpu_callback(),
which is refered by the exportet function padata_alloc().

This could lead to problems if CONFIG_HOTPLUG_CPU is disabled,
which should happen very often.

WARNING: kernel/built-in.o(.text+0x7ffcb): Section mismatch in reference from the function padata_alloc() to the function .cpuinit.text:padata_cpu_callback()
The function padata_alloc() references
the function __cpuinit padata_cpu_callback().
This is often because padata_alloc lacks a __cpuinit
annotation or the annotation of padata_cpu_callback is wrong.

Signed-off-by: Henrik Kretzschmar <henne@nachtwindheim.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>