MLK-21078-3 soc: imx: enable RX interrupt for IPC response

For IPC communication, CPU will be busy polling MU RX channel
after sending IPC message if IPC response is needed, such
mechanism wastes too much CPU resource if SCU takes long time
to finish the IPC request, so now enable RX interrupt for IPC
response.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Bai Ping <ping.bai@nxp.com>