x86/mm: Use PAGE_ALIGNED instead of IS_ALIGNED

Use PAGE_ALIGEND macro in <linux/mm.h> to simplify code.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: <guohanjun@huawei.com>
Cc: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1452565170-11083-1-git-send-email-wangkefeng.wang@huawei.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>