openssh: Don't create openssh-dev

populate_sdk installs all -dev packages, so having openssh-dev
pulls in openssh-sshd in as a dependency. That then conflicts with
Dropbear, which is only using openssh-sftp.

The openssh-dev package is empty and unused, created by bitbake.conf

Fixes https://github.com/openbmc/openbmc/issues/3819
related to
26dbcdb dropbear: use OpenSSH's sftp-server

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Change-Id: Ifce8207a5cd46c6d18d0eb82f3c7a9720616dd20
diff --git a/meta-phosphor/recipes-connectivity/openssh/openssh_%.bbappend b/meta-phosphor/recipes-connectivity/openssh/openssh_%.bbappend
new file mode 100644
index 0000000..72d59f6
--- /dev/null
+++ b/meta-phosphor/recipes-connectivity/openssh/openssh_%.bbappend
@@ -0,0 +1,4 @@
+# Don't create an empty openssh-dev package. That would pull in openssh-sshd
+# even it we are only depending on openssh-sftp, which causes conflicts
+# with dropbear
+ALLOW_EMPTY:${PN}-dev = "0"