tools: in ndnsec-key-gen, change default key type to ECDSA

Change-Id: Ib80da42d2969bb6288ee7949e6588c260476ef39
diff --git a/docs/manpages/ndnsec-key-gen.rst b/docs/manpages/ndnsec-key-gen.rst
index 6e18c20..2df5237 100644
--- a/docs/manpages/ndnsec-key-gen.rst
+++ b/docs/manpages/ndnsec-key-gen.rst
@@ -29,7 +29,7 @@
 
 .. option:: -t <type>, --type <type>
 
-   Type of key to generate. "r" for RSA (the default), "e" for ECDSA.
+   Type of key to generate. "r" for RSA, "e" for ECDSA (the default).
 
 .. option:: -k <keyidtype>, --keyid-type <keyidtype>