nfp: remove unused nfp_cpp_area_check_range()

Remove unused nfp_cpp_area_check_range() function.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>