PTR_ALIGN

The AdvanSys driver wants to align some pointers, and the ALIGN macro
doesn't work for pointers.  Rather than try to make it work, add a new
PTR_ALIGN macro which is typesafe.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>