padata - share code between CPU_ONLINE and CPU_DOWN_FAILED, same to CPU_DOWN_PREPARE and CPU_UP_CANCELED

Share code between CPU_ONLINE and CPU_DOWN_FAILED, same to
CPU_DOWN_PREPARE and CPU_UP_CANCELED.

It will fix 2 bugs:

  "not check the return value of __padata_remove_cpu() and __padata_add_cpu()".
  "need add 'break' between CPU_UP_CANCELED and CPU_DOWN_FAILED".
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Acked-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>