netconsole: switch init_netconsole() to late_initcall

Commit 88491d81

(drivers/net: Kconfig & Makefile cleanup) causes a
regression that netconsole does not work if netconsole and network
device driver are build into kernel, because netconsole is linked
before network device driver.

Andrew Morton suggested to fix this with initcall ordering.
Fixes it by switching init_netconsole() to late_initcall.

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>