staging: android: ion: Remove unused include files for ion_page_pool.c

After rewrite of ion_page_pool, some of its include file is no need
anymore, just remove it.

Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>