product/rdn2: add support for MCP firmware in rdn2

MCP ROM and RAM firmware, does not provide any specific functionality
yet. MCP ROM firmware loads the MCP RAM firmware which then executes
a WFI to enter idle state.

Change-Id: I6301601d9b3b60b5dc4e612c35ae5c765202b851
Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>