linux/mm.h: canonicalize macro PAGE_ALIGNED() definition

linux/mm.h: canonicalize macro PAGE_ALIGNED() definition

The macro PAGE_ALIGNED() is prone to cause error because it doesn't
follow convention to parenthesize parameter @addr within macro body, for
example unsigned long *ptr = kmalloc(...); PAGE_ALIGNED(ptr + 16); for
the left parameter of macro IS_ALIGNED(), (unsigned long)(ptr + 16) is
desired but the actual one is (unsigned long)ptr + 16.

It is fixed by simply canonicalizing macro PAGE_ALIGNED() definition.

Link: http://lkml.kernel.org/r/57EA6AE7.7090807@zoho.com
Signed-off-by: zijun_hu <zijun_hu@htc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>