cpumask: use cpumask_next_wrap() where appropriate

Now that cpumask_next{_and}_wrap() is wired to generic
find_next_bit_wrap(), we can use it in cpumask_any{_and}_distribute().

This automatically makes the cpumask_*_distribute() functions to use
small_cpumask_bits instead of nr_cpumask_bits, which itself is a good
optimization.

Signed-off-by: Yury Norov <yury.norov@gmail.com>