fix(versal2): add external declaration

This corrects the MISRA violation C2012-8.4:
A compatible declaration shall be visible when an object or
function with external linkage is defined.

Change-Id: I75c8e6a23ec192417f0e09c226f53c922a43f33c
Signed-off-by: Maheedhar Bollapalli <maheedharsai.bollapalli@amd.com>
diff --git a/plat/amd/versal2/include/scmi.h b/plat/amd/versal2/include/scmi.h
index 0ab8b34..761535b 100644
--- a/plat/amd/versal2/include/scmi.h
+++ b/plat/amd/versal2/include/scmi.h
@@ -14,6 +14,14 @@
 
 void init_scmi_server(void);
 
+size_t plat_scmi_pd_count(unsigned int agent_id);
+const char *plat_scmi_pd_get_name(unsigned int agent_id, unsigned int pd_id);
+unsigned int plat_scmi_pd_statistics(unsigned int agent_id, unsigned long *pd_id);
+unsigned int plat_scmi_pd_get_attributes(unsigned int agent_id, unsigned int pd_id);
+unsigned int plat_scmi_pd_get_state(unsigned int agent_id, unsigned int pd_id);
+int32_t plat_scmi_pd_set_state(unsigned int agent_id, unsigned int flags, unsigned int pd_id,
+				unsigned int state);
+
 #define SCMI_VENDOR	"AMD"
 #define SCMI_PRODUCT	"Versal Gen 2"