Remove empty states

In order to make the output more readable, I may be useful to not display the C-states/P-states where no events happen.

Eg.

    cpu2@state hits total(us) avg(us) min(us) max(us)
         POLL 0 0.00 0.00 0.00 0.00
         C1-IVB 210 66145.00 314.98 5.00 3643.00
         C3-IVB 292 112081.00 383.84 2.00 10010.00
         C6-IVB 3 170.00 56.67 53.00 60.00
         C7-IVB 681 2694581.00 3956.80 6.00 80158.00
         2901 0 0.00 0.00 0.00 0.00
         2900 0 0.00 0.00 0.00 0.00
         2800 0 0.00 0.00 0.00 0.00
         2700 0 0.00 0.00 0.00 0.00
         2500 0 0.00 0.00 0.00 0.00
         2400 0 0.00 0.00 0.00 0.00
         2300 0 0.00 0.00 0.00 0.00
         2200 0 0.00 0.00 0.00 0.00
         2000 0 0.00 0.00 0.00 0.00
         1900 0 0.00 0.00 0.00 0.00
         1800 0 0.00 0.00 0.00 0.00
         1700 0 0.00 0.00 0.00 0.00
         1600 0 0.00 0.00 0.00 0.00
         1400 0 0.00 0.00 0.00 0.00
         1300 0 0.00 0.00 0.00 0.00
         1200 0 0.00 0.00 0.00 0.00
    cpu2 wakeups name count

Becomes:

    cpu2@state hits total(us) avg(us) min(us) max(us)
         C1-IVB 210 66145.00 314.98 5.00 3643.00
         C3-IVB 292 112081.00 383.84 2.00 10010.00
         C6-IVB 3 170.00 56.67 53.00 60.00
         C7-IVB 681 2694581.00 3956.80 6.00 80158.00