slub: make slab_index() return unsigned int

slub: make slab_index() return unsigned int

slab_index() returns index of an object within a slab which is at most
u15 (or u16?).

Iterators additionally guarantee that "p >= addr".

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Alexey Dobriyan <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>