mm, memory_hotplug: drop pointless block alignment checks from __offline_pages

mainline inclusion
from mainline-5.0-rc1
commit 6cc2baf6
category: bugfix
bugzilla: 13472
CVE: NA

------------------------------------------------

This function is never called from a context which would provide
misaligned pfn range so drop the pointless check.

Link: http://lkml.kernel.org/r/20181107101830.17405-4-mhocko@kernel.org


Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Oscar Salvador <OSalvador@suse.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>