tools/funccount: support funccount on specified CPU (#3059)

A typical case of this feature: count timer setting on a x86 server
for each CPU:
 for i in `seq 0 39`;
   do ./funccount.py -i 1 lapic_next_deadline -d 5 -c $i;
 done

Then we can know the timer setting is balanced of not and do some
futher work.

Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>