cpumask: Remove unnecessary cpumask_nth_andnot()

Commit 94f75314("x86/resctrl: Optimize cpumask_any_housekeeping()")
switched the only user of cpumask_nth_andnot() to other cpumask
functions, but left the function cpumask_nth_andnot() unused.
This makes function find_nth_andnot_bit() unused as well. Delete them.

Signed-off-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>