ipsec-tools: use select rather than depends for library dependencies

As noticed on the mailing list.

package/ipsec-tools/Config.in

@@ -1,12 +1,11 @@
 config BR2_PACKAGE_IPSEC_TOOLS
 	bool "ipsec-tools"
-	depends on BR2_PACKAGE_OPENSSL && BR2_PACKAGE_FLEX && BR2_PACKAGE_FLEX_LIBFL
+	select BR2_PACKAGE_OPENSSL
+	select BR2_PACKAGE_FLEX
+	select BR2_PACKAGE_FLEX_LIBFL
 	help
 	  This package is required to support IPSec for Linux 2.6+
 
-comment "ipsec-tools	- disabled (requires openssl, flex and the flex library (libfl.a) )"
-	depends on !BR2_PACKAGE_OPENSSL || !BR2_PACKAGE_FLEX
-
 config BR2_PACKAGE_IPSEC_TOOLS_ADMINPORT
 	default y
 	depends on BR2_PACKAGE_IPSEC_TOOLS