Add the DIV_ROUND_UP() helper macro: divide `n' by `d', rounding up.

Stolen from the gfs2 tree(!) because the swsusp patches need it.
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>