staging: octeon-ethernet: drop CONFIG_CAVIUM_OCTEON_NUM_PACKET_BUFFERS

We don't have such Kconfig option, so the current code is dead and
the documentation is wrong. Users can adjust this setting by using
module parameter or kernel command line, so we can delete this code.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>