slp_parser: fix missing-field-initializers warnings

By attempting to pass a single field value into the Message,
the implication is that the other fields are non-initialized, due
to list-initialization rules.  Remove the first `0` parameter, so
that the default initialization is done.

Change-Id: If85a39c8c34299ec508edd888c052f622a463770
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/slp_parser.cpp b/slp_parser.cpp
index f6f85db..4c008ad 100644
--- a/slp_parser.cpp
+++ b/slp_parser.cpp
@@ -30,7 +30,7 @@
        |      Language Tag Length      |         Language Tag          \
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ */
 
-    Message req{0};
+    Message req{};
     int rc = slp::SUCCESS;
 
     std::copy_n(buff.data(), slp::header::SIZE_VERSION, &req.header.version);