netpoll: expose netpoll logging macros in public header

netpoll: expose netpoll logging macros in public header

Move np_info(), np_err(), and np_notice() macros from internal
implementation to the public netpoll header file to make them
available for use by netpoll consumers.

These logging macros provide consistent formatting for netpoll-related
messages by automatically prefixing log output with the netpoll instance
name.

The goal is to use the exact same format that is being displayed today,
instead of creating something netconsole-specific.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250613-rework-v3-2-0752bf2e6912@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>