ip: error out if iplink does not consume all options

ip: error out if iplink does not consume all options

dummy does not define .parse_opt, which make ip ignore all
trailing arguments, for example:

 # ip link add type dummy a b c d e f name cheese

will work just fine (and won't call the device "cheese").
Error out in this case with a clear error message:

 # ip link add type dummy a b c d e f name cheese
 Garbage instead of arguments "a ...". Try "ip link help".

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>