um: Prevent building modules incompatible with MODVERSIONS

The manual ld invocation in arch/um/drivers doesn't play nicely with
genksyms. Given the problematic modules are deprecated anyway, just
prevent building them when using MODVERSIONS.

e.g.
MODPOST Module.symvers
arch/um/drivers/.pcap.o.cmd: No such file or directory
Signed-off-by: Peter Foley <pefoley2@pefoley.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/Kconfig

@@ -261,6 +261,7 @@ config UML_NET_VECTOR
 config UML_NET_VDE
 	bool "VDE transport (obsolete)"
 	depends on UML_NET
+	depends on !MODVERSIONS
 	select MAY_HAVE_RUNTIME_DEPS
 	help
 	  This User-Mode Linux network transport allows one or more running
@@ -309,6 +310,7 @@ config UML_NET_MCAST
 config UML_NET_PCAP
 	bool "pcap transport (obsolete)"
 	depends on UML_NET
+	depends on !MODVERSIONS
 	select MAY_HAVE_RUNTIME_DEPS
 	help
 	  The pcap transport makes a pcap packet stream on the host look