mark Linux-specific configuration options

PLATFORM_LINUX is used as a dependency for applets or features
which require Linux-specific interfaces.

Signed-off-by: Jeremie Koenig <jk@jk.fr.eu.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/udhcp/Config.src b/networking/udhcp/Config.src
index aac8856..331dffc 100644
--- a/networking/udhcp/Config.src
+++ b/networking/udhcp/Config.src
@@ -8,6 +8,7 @@
 config UDHCPD
 	bool "udhcp server (udhcpd)"
 	default y
+	depends on PLATFORM_LINUX
 	help
 	  udhcpd is a DHCP server geared primarily toward embedded systems,
 	  while striving to be fully functional and RFC compliant.
@@ -51,6 +52,7 @@
 config UDHCPC
 	bool "udhcp client (udhcpc)"
 	default y
+	depends on PLATFORM_LINUX
 	help
 	  udhcpc is a DHCP client geared primarily toward embedded systems,
 	  while striving to be fully functional and RFC compliant.