ifpps: Rename cpu number parameter to stats_top()

This is not the top number of CPUs but the total number. Rename the
variable to not confuse this.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
ifpps: minor: fix ncurses alignment

Since we've added '+'/'-' for max/min CPU values, we also need to shift
once whitespace to the left to properly align ncurses display again.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>