net: Revert ARCNET and PHYLIB to tristate options

commit 88491d8103498a6166f70d5999902fec70924314 ("drivers/net: Kconfig
& Makefile cleanup") changed the type of these options to bool, but
they select code that could (and still can) be built as modules.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/arcnet/Kconfig b/drivers/net/arcnet/Kconfig
index a73d9dc..84fb634 100644
--- a/drivers/net/arcnet/Kconfig
+++ b/drivers/net/arcnet/Kconfig
@@ -4,7 +4,7 @@
 
 menuconfig ARCNET
 	depends on NETDEVICES && (ISA || PCI || PCMCIA)
-	bool "ARCnet support"
+	tristate "ARCnet support"
 	---help---
 	  If you have a network card of this type, say Y and check out the
 	  (arguably) beautiful poetry in