refactor(ff-a): replace `plat_ffa_` prefix for public functions

Replace `plat_ffa_` prefix with `ffa_{file_name}_` prefix. Only do so
for public functions to avoid unnecessary churn (private functions are
renamed in the next commit).

Change-Id: I847c218f134a2519a45a3af1d6c4b953db9c1cbb
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/src/arch/aarch64/hypervisor/handler.c b/src/arch/aarch64/hypervisor/handler.c
index 5e32a1e..2328d41 100644
--- a/src/arch/aarch64/hypervisor/handler.c
+++ b/src/arch/aarch64/hypervisor/handler.c
@@ -731,7 +731,7 @@
 		*args = api_ffa_console_log(*args, current);
 		return true;
 	case FFA_ERROR_32:
-		*args = plat_ffa_error_32(current, next, args->arg2);
+		*args = ffa_cpu_cycles_error_32(current, next, args->arg2);
 		return true;
 
 	default: