drivers: move scmi-msg out of st

Make the scmi-msg driver reused by others.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Change-Id: I5bc35fd4dab70f45c09b8aab65af4209cf23b124
diff --git a/plat/st/stm32mp1/services/stm32mp1_svc_setup.c b/plat/st/stm32mp1/services/stm32mp1_svc_setup.c
index 49375a6..d4ed445 100644
--- a/plat/st/stm32mp1/services/stm32mp1_svc_setup.c
+++ b/plat/st/stm32mp1/services/stm32mp1_svc_setup.c
@@ -9,7 +9,7 @@
 
 #include <common/debug.h>
 #include <common/runtime_svc.h>
-#include <drivers/st/scmi-msg.h>
+#include <drivers/scmi-msg.h>
 #include <lib/psci/psci.h>
 #include <tools_share/uuid.h>