rbd: make const pointer spaces a static const array

Don't populate the const array spaces on the stack but make it static
const and make the pointer an array to remove a dereference. Shrinks
object code a little too.  Also clean up intent, currently it is spaces
and should be a tab.

Signed-off-by: Colin Ian King <colin.i.king@googlemail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>