lib/bitmap: introduce for_each_set_bit_wrap() macro

Add for_each_set_bit_wrap() macro and use it in for_each_cpu_wrap(). The
new macro is based on __for_each_wrap() iterator, which is simpler and
smaller than cpumask_next_wrap().

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