security/openssh-portable: Add comment in openssh.in about host keys

Commit ae66cffc19 added some rc vars to allow disabling host keys.
The naming caused some confusion. Attempt to address that with a
comment since these are not documented anywhere else.

PR:	        202169

security/openssh-portable/Makefile

@@ -2,7 +2,7 @@
 
 PORTNAME=	openssh
 DISTVERSION=	8.9p1
-PORTREVISION=	2
+PORTREVISION=	3
 PORTEPOCH=	1
 CATEGORIES=	security
 MASTER_SITES=	OPENBSD/OpenSSH/portable

security/openssh-portable/files/openssh.in

@@ -22,6 +22,7 @@ load_rc_config ${name}
 : ${openssh_enable:="NO"}
 : ${openssh_skipportscheck="NO"}
 
+# These only control ssh-keygen automatically generating host keys.
 : ${openssh_dsa_enable="YES"}
 : ${openssh_dsa_flags=""}
 : ${openssh_rsa_enable="YES"}