netpoll: move netpoll_print_options to netconsole

netpoll: move netpoll_print_options to netconsole

Move netpoll_print_options() from net/core/netpoll.c to
drivers/net/netconsole.c and make it static. This function is only used
by netconsole, so there's no need to export it or keep it in the public
netpoll API.

This reduces the netpoll API surface and improves code locality
by keeping netconsole-specific functionality within the netconsole
driver.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250613-rework-v3-4-0752bf2e6912@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>