include: Move instance-id.h under libpldm/

The installed location for the header is
`${includedir}/libpldm/instance-id.h`. Make the in-tree location
equivalent so we don't have a slightly jarring inconsistency.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I9c1f324e18ba504261845187e88e35db0d8ef873
diff --git a/src/requester/instance-id.c b/src/requester/instance-id.c
index e3cf41f..3d39fd8 100644
--- a/src/requester/instance-id.c
+++ b/src/requester/instance-id.c
@@ -1,6 +1,6 @@
 // NOLINTNEXTLINE(bugprone-reserved-identifier,cert-dcl37-c,cert-dcl51-cpp)
 #define _GNU_SOURCE
-#include "libpldm/requester/instance-id.h"
+#include "libpldm/instance-id.h"
 #include "libpldm/pldm.h"
 #include <errno.h>
 #include <fcntl.h>