netpoll: relocate netconsole-specific functions to netconsole module

netpoll: relocate netconsole-specific functions to netconsole module

Move netpoll_parse_ip_addr() and netpoll_parse_options() from the generic
netpoll module to the netconsole module where they are actually used.

These functions were originally placed in netpoll but are only consumed by
netconsole. This refactoring improves code organization by:

 - Removing unnecessary exported symbols from netpoll
 - Making netpoll_parse_options() static (no longer needs global visibility)
 - Reducing coupling between netpoll and netconsole modules

The functions remain functionally identical - this is purely a code
reorganization to better reflect their actual usage patterns. Here are
the changes:

 1) Move both functions from netpoll to netconsole
 2) Add static to netpoll_parse_options()
 3) Removed the EXPORT_SYMBOL()

PS: This diff does not change the function format, so, it is easy to
review, but, checkpatch will not be happy. A follow-up patch will
address the current issues reported by checkpatch.

Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250613-rework-v3-3-0752bf2e6912@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>