Fix mki issues

1. Set correct mki from the `use_srtp` extension.
2. Use mki value received from the client as the mki used by server.
3. Use `mbedtls_ssl_dtls_srtp_set_mki_value()` as a client API only.

Signed-off-by: Johan Pascal <johan.pascal@belledonne-communications.com>
diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 4073f89..7d9c9c3 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -1851,7 +1851,7 @@
     if (((uint16_t)( ( buf[0]<<8 ) | buf[1] ) ) != 0x0002) { /* protection profile length must be 0x0002 as we must have only one protection profile in server Hello */
         return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
     } else {
-        server_protection_profile_value = ( buf[2]<<8 ) | buf[3];
+        server_protection_profile_value = ( buf[2] << 8 ) | buf[3];
     }
 
     ssl->dtls_srtp_info.chosen_dtls_srtp_profile = MBEDTLS_SRTP_UNSET_PROFILE;