mm/page_alloc: remove unused parameter in init_currently_empty_zone()

mm/page_alloc: remove unused parameter in init_currently_empty_zone()

Commit a2f3aa02576632cdb ("[PATCH] Fix sparsemem on Cell") fixed an oops
experienced on the Cell architecture when init-time functions, early_*(),
are called at runtime by introducing an 'enum memmap_context' parameter to
memmap_init_zone() and init_currently_empty_zone().  This parameter is
intended to be used to tell whether the call of these two functions is
being made on behalf of a hotplug event, or happening at boot-time.
However, init_currently_empty_zone() does not use this parameter at all,
so remove it.

Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>