fix: error return in FFA_MEM_PERM_GET/SET

After initilisation the FFA_MEM_PERM_GET/SET shall not
be used.
The error code to use in case the interface is used after
initilisation shall be FFA_DENIED.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I58ccd9e110f18ad879e36f5584387040fa6d8f19
diff --git a/src/api.c b/src/api.c
index 2b732ff..762b6bb 100644
--- a/src/api.c
+++ b/src/api.c
@@ -4218,7 +4218,7 @@
 	uint32_t mode = 0;
 
 	if (!plat_ffa_is_mem_perm_get_valid(current)) {
-		return ffa_error(FFA_NOT_SUPPORTED);
+		return ffa_error(FFA_DENIED);
 	}
 
 	if (!(current->vm->el0_partition)) {
@@ -4283,7 +4283,7 @@
 	struct mpool local_page_pool;
 
 	if (!plat_ffa_is_mem_perm_set_valid(current)) {
-		return ffa_error(FFA_NOT_SUPPORTED);
+		return ffa_error(FFA_DENIED);
 	}
 
 	if (!(current->vm->el0_partition)) {