lib/prog_loaders: Move argument selection into selfload

Set the payload argument in selfload, as other (non self) payloads, are
going to set a different argument.

Change-Id: I994f604fc4501e0e3b00165819f796b1b8275d8c
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/25861
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/arm64/arm_tf.c

@@ -51,9 +51,9 @@ void arm_tf_run_bl31(u64 payload_entry, u64 payload_arg0, u64 payload_spsr)
 	if (prog_locate(&bl31))
 		die("BL31 not found");
 
-	bl31_entry = selfload(&bl31, false);
-	if (!bl31_entry)
+	if (!selfload(&bl31, false))
 		die("BL31 load failed");
+	bl31_entry = prog_entry(&bl31);
 
 	SET_PARAM_HEAD(&bl31_params, PARAM_BL31, VERSION_1, 0);