Copying keys into /cfg automatically

The idea here is to copy the SSH key material which gets generated
during the first boot into a persistent place. That way, one can update
the system freely, and the SSH keys for both OpenSSH and Netopeer2's
server/keystored will be preserved.

Change-Id: I094ab3142195ce4dd5e714b486962b2ec4925098
diff --git a/package/czechlight-cfg-fs/Config.in b/package/czechlight-cfg-fs/Config.in
index 3974d6c..81fe19f 100644
--- a/package/czechlight-cfg-fs/Config.in
+++ b/package/czechlight-cfg-fs/Config.in
@@ -27,4 +27,14 @@
 
 endif # BR2_PACKAGE_SYSREPO
 
+if BR2_PACKAGE_NETOPEER2_KEYSTORED
+
+config CZECHLIGHT_CFG_FS_PERSIST_KEYS
+	bool "Persist host keys for OpenSSH and Netopeer2"
+	default Y
+	help
+	  Save OpenSSH's key material and netopeer2-keystored's SSH keys into /cfg
+
+endif # BR2_PACKAGE_NETOPEER2_KEYSTORED
+
 endif # BR2_PACKAGE_CZECHLIGHT_CFG_FS