refactor: mailbox doesn't need size and sender

The mailbox structure doesn't need to keep track of the
sender ID and the size for memory sharing ABIs.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: If1a7731c9cbaab04360a5ffeb4be4a8342b50280
diff --git a/src/ffa_memory.c b/src/ffa_memory.c
index 8641d5b..504308c 100644
--- a/src/ffa_memory.c
+++ b/src/ffa_memory.c
@@ -3263,8 +3263,7 @@
 		share_state->fragment_constituent_counts[fragment_index],
 		&fragment_length);
 	CHECK(remaining_constituent_count == 0);
-	to_locked.vm->mailbox.recv_size = fragment_length;
-	to_locked.vm->mailbox.recv_sender = HF_HYPERVISOR_VM_ID;
+
 	to_locked.vm->mailbox.recv_func = FFA_MEM_FRAG_TX_32;
 	to_locked.vm->mailbox.state = MAILBOX_STATE_FULL;