drivers/char/ip2: fix Kconfig after ip2/ip2main merge

As commit 6089093e ("ip2: fix crashes on
load/unload") fixed the ip2 crashes on load/unload by making ip2/ip2main
one module (ip2), Kconfig shouldn't mention a now non-existing module.

Signed-off-by: Roland.Kletzing <devzero@web.de>
Acked-by: Alan Cox <alan@redhat.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>