Rename ssl_cli/srv.c

Rename ssl_cli.c and ssl_srv.c to reflect the fact
that they are TLS 1.2 specific now. Align there new
names with the TLS 1.3 ones.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index ddede03..6c3d7fd 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -99,12 +99,12 @@
     net_sockets.c
     ssl_cache.c
     ssl_ciphersuites.c
-    ssl_cli.c
     ssl_cookie.c
     ssl_msg.c
-    ssl_srv.c
     ssl_ticket.c
     ssl_tls.c
+    ssl_tls12_client.c
+    ssl_tls12_server.c
     ssl_tls13_keys.c
     ssl_tls13_server.c
     ssl_tls13_client.c