refactor: rename type for FF-A IDs

The FF-A ID is a unsigned 16-bit value that was named
ffa_vm_id_t. This patch changes it to simply ffa_id_t.
This is to make clearer the ID type is used for other
endpoints other than simply VMs.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I60319c08481b2380bd0063b108a35fc01e2af537
diff --git a/inc/hf/dlog.h b/inc/hf/dlog.h
index 9147549..99b10de 100644
--- a/inc/hf/dlog.h
+++ b/inc/hf/dlog.h
@@ -74,4 +74,4 @@
 		}                                      \
 	} while (0)
 
-void dlog_flush_vm_buffer(ffa_vm_id_t id, char buffer[], size_t length);
+void dlog_flush_vm_buffer(ffa_id_t id, char buffer[], size_t length);