ifpps: min: minor: Keep options sorted alphabetically

Keep the options sorted alphabetically, argument options first.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
ifpps: Mark omit_header parameter to screen_main() as unused

Otherwise we get a warning when compiling with "-W -Wall".

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
ifpps: Simplify logic wrt. omit_header in term_main()

We can reuse the omit_header variable to get rid of the existing
variable 'first', which was used to make sure the header gets only
printed once at the beginning.

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