ipx: remove the BKL

This replaces all instances of lock_kernel in the
IPX code with lock_sock. As far as I can tell, this
is safe to do, because there is no global state
that needs to be locked in IPX, and the code does
not recursively take the lock or sleep indefinitely
while holding it.

Compile-tested only.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: netdev@vger.kernel.org