ifpps: Use unsigned int to store number of CPUs

Since get_number_cpus() now returns unsigned int store it's return value
and derived values in unsigned int variables as well.

This fixes the some warnings when compiling with -W/-Wsign-compare:

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
ifpps: Remove unused parameter to term_csv()

term_csv() doesn't use the ifname and ms_interval parameters, they're
only used in term_csv_header(). Thus remove them from term_csv().

This fixes a warning when compiling with -W/-Wunused-parameter.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>